Improve thread IDs to avoid collisions with threads not created by the Godot API.

[bruvzg]

Replaces custom thread IDs with std::thread::id hashes.

Fixes #46679, fixes #46550 and fixes #46411

[akien-mga]

Thanks!

[akien-mga]

Cherry-picked for 3.2.4.

[akien-mga]

Undid my cherry-pick for now (hadn't pushed yet) as it doesn't seem to work as is in 3.2:

[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
WARNING: start: A Thread object has been re-started without wait_to_finish() having been called on it. Please do so to ensure correct cleanup of the thread.
   At: core/os/thread.cpp:82.
terminate called after throwing an instance of 'std::system_error'
  what():  Invalid argument

Program received signal SIGABRT, Aborted.
0x00007ffff7aa04b0 in raise () from /lib64/libc.so.6
Missing separate debuginfos, use: debuginfo-install lib64bsd0-0.10.0-2.mga8.x86_64 lib64gl1-1.3.2-16.mga8.x86_64 lib64glx0-1.3.2-16.mga8.x86_64 lib64x11_6-1.7.0-1.mga8.x86_64 lib64xau6-1.0.9-2.mga8.x86_64 lib64xcb1-1.14-1.mga8.x86_64 lib64xcursor1-1.2.0-2.mga8.x86_64 lib64xdmcp6-1.1.3-2.mga8.x86_64 lib64xext6-1.3.4-2.mga8.x86_64 lib64xfixes3-5.0.3-3.mga8.x86_64 lib64xi6-1.7.10-2.mga8.x86_64 lib64xinerama1-1.1.4-3.mga8.x86_64 lib64xrandr2-1.5.2-2.mga8.x86_64 lib64xrender1-0.9.10-3.mga8.x86_64
(gdb) bt
#0  0x00007ffff7aa04b0 in raise () from /lib64/libc.so.6
#1  0x00007ffff7a8b526 in abort () from /lib64/libc.so.6
#2  0x0000000001702e2b in __gnu_cxx::__verbose_terminate_handler () at ../../../../libstdc++-v3/libsupc++/vterminate.cc:95
#3  0x00000000046eb696 in __cxxabiv1::__terminate (handler=<optimized out>) at ../../../../libstdc++-v3/libsupc++/eh_terminate.cc:48
#4  0x00000000046eb701 in std::terminate () at ../../../../libstdc++-v3/libsupc++/eh_terminate.cc:58
#5  0x00000000046eb854 in __cxxabiv1::__cxa_throw (obj=obj@entry=0x673e9a0, tinfo=tinfo@entry=0x60cb4e8 <typeinfo for std::system_error>, dest=dest@entry=0x4764820 <std::system_error::~system_error()>)
    at ../../../../libstdc++-v3/libsupc++/eh_throw.cc:95
#6  0x0000000001704c2f in std::__throw_system_error (__i=22) at ../../../../../libstdc++-v3/src/c++11/system_error.cc:338
#7  0x0000000004764d3a in std::thread::detach (this=0x673e8f0) at ../../../../../libstdc++-v3/src/c++11/thread.cc:127
#8  0x00000000043ca577 in Thread::start (this=0x673e8e8, p_callback=0x445cd2b <_IP_ResolverPrivate::_thread_function(void*)>, p_user=0x673e360, p_settings=...) at core/os/thread.cpp:84
#9  0x000000000445c520 in IP::IP (this=0x6725020) at core/io/ip.cpp:319
#10 0x00000000028f666b in IP_Unix::IP_Unix (this=0x6725020) at drivers/unix/ip_unix.cpp:265
#11 0x00000000028f6637 in IP_Unix::_create_unix () at drivers/unix/ip_unix.cpp:262
#12 0x000000000445c44c in IP::create () at core/io/ip.cpp:310
#13 0x00000000042bb622 in register_core_types () at core/register_core_types.cpp:212
#14 0x000000000173db89 in Main::setup (execpath=0x7fffffffdbcb "/home/akien/.local/bin/godot-3.2", argc=0, argv=0x7fffffffd790, p_second_phase=true) at main/main.cpp:361
#15 0x00000000017056f8 in main (argc=1, argv=0x7fffffffd788) at platform/x11/godot_x11.cpp:49

[bruvzg]

Undid my cherry-pick for now (hadn't pushed yet) as it doesn't seem to work as is in 3.2:

3.2 have ID initialized in the constructor, it's probably not cherry-picked correctly, and override it with zero.
PR for 3.2: #46749.