[Bug #20342] Consider wrapped load in `main` methods

* Reword Range#overlap? docs last paragraph.

* Docs: add explanation about Queue#freeze

* Docs: Add :rescue event docs for TracePoint

* Docs: Enhance Module#set_temporary_name documentation

* Docs: Slightly expand Process::Status deprecations

* Fix MatchData#named_captures rendering glitch

* Improve Dir.fchdir examples

* Adjust Refinement#target docs

This patch introduce M:N thread scheduler for Ractor system.

In general, M:N thread scheduler employs N native threads (OS threads)
to manage M user-level threads (Ruby threads in this case).
On the Ruby interpreter, 1 native thread is provided for 1 Ractor
and all Ruby threads are managed by the native thread.

From Ruby 1.9, the interpreter uses 1:1 thread scheduler which means
1 Ruby thread has 1 native thread. M:N scheduler change this strategy.

Because of compatibility issue (and stableness issue of the implementation)
main Ractor doesn't use M:N scheduler on default. On the other words,
threads on the main Ractor will be managed with 1:1 thread scheduler.

There are additional settings by environment variables:

`RUBY_MN_THREADS=1` enables M:N thread scheduler on the main ractor.
Note that non-main ractors use the M:N scheduler without this
configuration. With this configuration, single ractor applications
run threads on M:1 thread scheduler (green threads, user-level threads).

`RUBY_MAX_CPU=n` specifies maximum number of native threads for
M:N scheduler (default: 8).

This patch will be reverted soon if non-easy issues are found.

[Bug #19842]

[Feature #19714]

From Ruby 3.0, refined method invocations are slow because
resolved methods are not cached by inline cache because of
conservertive strategy. However, `using` clears all caches
so that it seems safe to cache resolved method entries.

This patch caches resolved method entries in inline cache
and clear all of inline method caches when `using` is called.

fix [Bug #18572]

```ruby
 # without refinements

class C
  def foo = :C
end

N = 1_000_000

obj = C.new
require 'benchmark'
Benchmark.bm{|x|
  x.report{N.times{
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
  }}
}

_END__
              user     system      total        real
master    0.362859   0.002544   0.365403 (  0.365424)
modified  0.357251   0.000000   0.357251 (  0.357258)
```

```ruby
 # with refinment but without using

class C
  def foo = :C
end

module R
  refine C do
    def foo = :R
  end
end

N = 1_000_000

obj = C.new
require 'benchmark'
Benchmark.bm{|x|
  x.report{N.times{
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
  }}
}
__END__
               user     system      total        real
master     0.957182   0.000000   0.957182 (  0.957212)
modified   0.359228   0.000000   0.359228 (  0.359238)
```

```ruby
 # with using

class C
  def foo = :C
end

module R
  refine C do
    def foo = :R
  end
end

N = 1_000_000

using R

obj = C.new
require 'benchmark'
Benchmark.bm{|x|
  x.report{N.times{
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
    obj.foo; obj.foo; obj.foo; obj.foo; obj.foo;
  }}
}

[Bug #19593]

rb_ec_setup_exception did not check if errinfo is a throw_data. This can
cause crashes in code since it is assumed that id_cause is an object.

We saw a crash in show_cause due to id_cause of errinfo being a
throw_data. It crashes on rb_obj_is_kind_of since it cannot be called on
T_IMEMO objects.

Unfortunately, we couldn't find a reproduction script, however we
debugged the core dump and rb_ec_setup_exception is the only place where
id_cause is assigned from errinfo without checking if it is a
throw_data.

```
0x0000556c5708e6dd in sigsegv (sig=11, info=0x7f301befa3f0, ctx=0x7f301befa2c0) at signal.c:964
0x00007f301d046420 in <signal handler called> () at /lib/x86_64-linux-gnu/libpthread.so.0
class_search_class_ancestor (c=139844586301760, cl=<optimized out>) at object.c:810
rb_obj_is_kind_of (obj=obj@entry=139839221734880, c=139844586301760) at object.c:861
0x0000556c56f2f00f in show_cause
    (errinfo=errinfo@entry=139838840645160, str=str@entry=139839221730520, opt=139839221730480, highlight=0, reverse=reverse@entry=0, backtrace_limit=backtrace_limit@entry=-1, shown_causes=0x7ffe9d1a2d68) at ./include/ruby/internal/special_consts.h:175
```

Co-Authored-By: Jean Boussier <byroot@ruby-lang.org>

Right now the attached object is stored as an instance variable
and all the call sites that either get or set it have to know how it's
stored.

It's preferable to hide this implementation detail behind accessors
so that it is easier to change how it's stored.

[Feature #19425]