check.sh: add logic to detect "SCRIPT ERROR" + memory leaks, like in CI

[Bromeon]

I noticed during #1466 that a CI error couldn't be reproduced locally. It was visible in logs, but not obvious to find, as tests kept running after the error. Basically, when GDScript causes a SCRIPT ERROR, this is externally detected (using tee + grep).

So this PR copy-pastes the CI logic to check.sh, with minor changes to fit the local environment. Maybe in the future we can use Logger to detect this from within godot-rust.

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-1468

[Yarwin]

Suggested change

	# Below logic to abort immediately if Godot outputs certain keywords (would otherwise fail only in CI).
	# Logic to abort immediately if Godot outputs certain keywords (would otherwise fail only in CI).

[Yarwin]

Suggested change

	# Keep in sync with: .github/composite/godot-itest/action.yml (steps "Run Godot integration tests" and "Check for memory leaks")
	# Keep in sync with: .github/composite/godot-itest/action.yml (steps "Run Godot integration tests" and "Check for memory leaks").

[Yarwin]

Suggested change

	# * tee: still output logs while scanning for errors
	# * grep -q: no output, use exit code 0 if found -> thus also &&
	# * pkill: stop Godot execution (since it hangs in headless mode); simple 'head -1' did not work as expected
	# since it's not available on Windows, use taskkill in that case.
	# * exit: the terminated process would return 143, but this is more explicit and future-proof
	# * tee: still output logs while scanning for errors.
	# * grep -q: no output, use exit code 0 if found -> thus also &&.
	# * pkill: stop Godot execution (since it hangs in headless mode); simple 'head -1' did not work as expected
	# since it's not available on Windows, use taskkill in that case.
	# * exit: the terminated process would return 143, but this is more explicit and future-proof.