Panic handling: thread safety; set hook once and not repeatedly #3353

Job	Run time
license-guard	30s
doc-lints	48s
clippy	1m 50s
godot-itest (macos)	59s
godot-itest (windows)	2m 7s
run-examples	1m 19s
rustfmt	18s
godot-itest (linux-full)	1m 21s
unit-test	2m 11s
godot-itest (linux-features-experimental)	1m 52s
godot-itest (linux-4.1)	1m 9s
godot-itest (linux-4.2)	1m 2s
godot-itest (linux-4.3)	1m 13s
godot-itest (linux-memcheck)	2m 13s
ci-status	1s
	18m 53s

Provide feedback