This change fixes a bug in which specifying 0 for timeout-related options (such as the `timeout` option of `Addrinfo.getaddrinfo`) incorrectly results in an infinite wait.

(This change overwrites https://github.com/ruby/ruby/pull/15626 .)

This change adds host information to the error messages shown when a timeout occurs while passing timeout options to `TCPSocket.new` or `Socket.tcp`, for improved usability.
(When the `fast_fallback option` is enabled, there may be multiple possible destinations, so the host name is shown instead of an IP address.)

As part of this change, the error messages in `Addrinfo.getaddrinfo` and `Addrinfo#connect_internal`, both of which are used by `Socket.tcp`, have also been improved in the same way.

We were seeing segfaults when calling `pthread_detach`. Apparently in
some versions of glibc there is a race between when this is called
(usually right after starting a thread) and a short-lived thread's
shutdown routine. The bug has been reported to glibc:

https://sourceware.org/bugzilla/show_bug.cgi?id=19951

I haven't been able to reproduce it on my Linux desktop but apparently
it's easier to reproduce on certain kinds of servers.

As a workaround, we can set the thread's detach state before thread
start. I don't know of a platform that doesn't have
`pthread_attr_setdetachstate`, but to be safe we check for it in
`extconf.rb` and use `pthread_detach` as a backup if it isn't available.

Fixes [Bug #21679]

On OpenBSD:

```
ld: warning: namespace.c:731(namespace.o:(rb_namespace_local_extension)): warning: strcpy() is almost always misused, please use strlcpy()
```

Similar to 19f3793a4bd6974cd66cc058fc6d2ae733337745

Fixes:

```
../../../ext/socket/raddrinfo.c:755:60: warning: implicit conversion loses integer precision: 'size_t' (aka 'unsigned long') to 'socklen_t' (aka 'unsigned int') [-Wshorten-64-to-32]
  755 |         return getnameinfo(sa, salen, host, hostlen, serv, servlen, flags);
      |                ~~~~~~~~~~~                                 ^~~~~~~
../../../ext/socket/raddrinfo.c:755:45: warning: implicit conversion loses integer precision: 'size_t' (aka 'unsigned long') to 'socklen_t' (aka 'unsigned int') [-Wshorten-64-to-32]
  755 |         return getnameinfo(sa, salen, host, hostlen, serv, servlen, flags);
      |                ~~~~~~~~~~~                  ^~~~~~~
```

When calling getnameinfo we spawn a thread because it may do a slow,
blocking reverse-DNS lookup. Spawning a thread is relatively fast (~20µs
on my Linux machine) but still an order of magnitude slower than when
getnameinfo is simply translating to a numeric IP or port, which, at
least in my tests on Linux, doesn't even make a syscall.

This commit adds a fast path for when reverse DNS isn't required: either
host isn't being fetched or NI_NUMERICHOST is set AND either the
service name isn't required or NI_NUMERICSERV is set. The service name
should only need to read /etc/services, which should be fast-ish, but
is still I/O so I kept the existing behaviour (it could be on a network
fs I guess).

I tested with:

    s = TCPSocket.open("www.ruby-lang.org", 80)
    500_000.times { Socket.unpack_sockaddr_in(s.getpeername) }

Before: 12.935s
After: 0.338s

* [Feature #21347] Add `open_timeout` as an overall timeout option for `TCPSocket.new`

With this change, `TCPSocket.new` now accepts the `open_timeout` option.
This option raises an exception if the specified number of seconds has elapsed since the start of the method call,
even if the operation is still in the middle of name resolution or connection attempts.

The addition of this option follows the same intent as the previously merged change to `Socket.tcp`.
[Feature #21347](https://bugs.ruby-lang.org/issues/21347)
https://github.com/ruby/ruby/pull/13368

* Tidy up: Extract rsock_raise_user_specified_timeout()

* Added a note to the documentation of `Socket.tcp`

* Fix `rsock_init_inetsock` for `FAST_FALLBACK_INIT_INETSOCK_IMPL`

This change addresses the following ASAN error:

```
==1973462==ERROR: AddressSanitizer: heap-use-after-free on address 0x5110002117dc at pc 0x749c307c8a65 bp 0x7ffc3af331d0 sp 0x7ffc3af331c8
READ of size 4 at 0x5110002117dc thread T0
    #0 0x749c307c8a64 in rb_getaddrinfo /tmp/ruby/src/trunk_asan/ext/socket/raddrinfo.c:564:14
    #1 0x749c307c8a64 in rsock_getaddrinfo /tmp/ruby/src/trunk_asan/ext/socket/raddrinfo.c:1008:21
    #2 0x749c307cac48 in rsock_addrinfo /tmp/ruby/src/trunk_asan/ext/socket/raddrinfo.c:1049:12
    #3 0x749c307b10ae in init_inetsock_internal /tmp/ruby/src/trunk_asan/ext/socket/ipsocket.c:62:23
    #4 0x562c5b2e327e in rb_ensure /tmp/ruby/src/trunk_asan/eval.c:1080:18
    #5 0x749c307aafd4 in rsock_init_inetsock /tmp/ruby/src/trunk_asan/ext/socket/ipsocket.c:1318:12
    #6 0x749c307b3b78 in tcp_svr_init /tmp/ruby/src/trunk_asan/ext/socket/tcpserver.c:39:12
```

Fixed to avoid accessing memory that has already been freed after calling `free_getaddrinfo_arg`.

[Bug #21506] Fix timeout in Addrinfo.getaddrinfo to actually take effect

This change fixes an issue where the timeout option in `Addrinfo.getaddrinfo` was not functioning as expected.

It also addresses a related issue where specifying `fast_fallback: false` with `resolv_timeout` for `Socket.tcp` and`TCPSocket.new` would have no effect.

The timeout option was originally introduced in:
https://github.com/ruby/ruby/commit/6382f5cc91ac9e36776bc854632d9a1237250da7

However, the value was noy used in current implementation:
https://github.com/ruby/ruby/blob/3f0e0d5c8bf9046aee7f262a3f9a7524d51aaf3e/ext/socket/raddrinfo.c#L1282-1308

Therefore, even if a timeout is specified and the duration elapses during name resolution, nothing happens. This is clearly not the intended behavior.

`Addrinfo.getaddrinfo` has been made interruptible as of Feature #19965.
This change uses that feature to interrupt name resolution when the specified timeout period elapses, raising a user-specified timeout error.
The timeout can be specified in milliseconds.

The same issue affects `Socket.tcp` and `TCPSocket.new` when `resolv_timeout` is set along with `fast_fallback: false`.
`resolv_timeout` was introduced in the following commits:
https://github.com/ruby/ruby/commit/6382f5cc91ac9e36776bc854632d9a1237250da7
https://github.com/ruby/ruby/commit/511fe23fa2bdf1f17faa91e0558be47b5bb62b2a

The reason is that with `fast_fallback: false`, these methods internally call the same `rsock_getaddrinfo()` as `Addrinfo.getaddrinfo`.
This change addresses that as well.