Add an OS.get_thread_caller_id() method

This can be used to print thread IDs in logs. This can make it easier
to debug multi-threaded applications.

Co-authored-by: Khaos <khaos@khaos-coders.org>

doc/classes/OS.xml

@@ -127,6 +127,14 @@
 				Returns the keycode of the given string (e.g. "Escape").
 			</description>
 		</method>
+		<method name="get_thread_caller_id" qualifiers="const">
+			<return type="int">
+			</return>
+			<description>
+				Returns the ID of the current thread. This can be used in logs to ease debugging of multi-threaded applications.
+				[b]Note:[/b] Thread IDs are not deterministic and may be reused across application restarts.
+			</description>
+		</method>
 		<method name="get_cmdline_args">
 			<return type="PackedStringArray">
 			</return>