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.

* `Socket.tcp` and `TCPSocket.new` raises `IO::TiemoutError` with user specified timeout

In https://github.com/ruby/ruby/pull/11880, `rsock_connect()` was changed to raise `IO::TimeoutError` when a user-specified timeout occurs.
However, when `TCPSocket.new` attempts to connect to multiple destinations, it does not use `rsock_connect()`, and instead raises `Errno::ETIMEDOUT` on timeout.
As a result, the exception class raised on timeout could differ depending on whether there were multiple destinations or not.

To align this behavior with the implementation of `rsock_connect()`, this change makes `TCPSocket.new` raise `IO::TimeoutError` when a user-specified timeout occurs.
Similarly, `Socket.tcp` is updated to raise `IO::TimeoutError` when a timeout occurs within the method.
(Note that the existing behavior of `Addrinfo#connect_internal`, which Socket.tcp depends on internally and which raises `Errno::ETIMEDOUT` on timeout, is not changed.)

* [ruby/net-http] Raise `Net::OpenTimeout` when `TCPSocket.open` raises `IO::TimeoutError`.

With the changes in https://github.com/ruby/ruby/pull/15602, `TCPSocket.open` now raises `IO::TimeoutError` when a user-specified timeout occurs.
This change updates #connect to handle this case accordingly.

https://github.com/ruby/net-http/commit/f64109e1cf

This change updates the behavior so that, when there is only a single destination and `open_timeout` is specified, the remaining `open_timeout` duration is used as the connection timeout.

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]

ipsocket.c:57:1: warning: old-style function definition [-Wold-style-definition]
   57 | current_clocktime()
      | ^~~~~~~~~~~~~~~~~

This suppresses this warning:

../../../ext/socket/ipsocket.c: In function ‘rsock_raise_user_specified_timeout’:
../../../ext/socket/ipsocket.c:30:1: warning: function might be candidate for attribute ‘noreturn’ [-Wsuggest-attribute=noreturn]
   30 | rsock_raise_user_specified_timeout()
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

* [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`