GDScript: Properly track extents of constants

[vnen]

Even in the case of errors.

• Fix Mismatch in extents tracking stack spam with a hanging const keyword #76054
• Fix Parser bug: Mismatch in extents tracking stack. #76564

Note: I did a check across the parser to see if any other of these would be missing and didn't find anything. I won't mind if someone else wants to double check.

Bugsquad edit: Issue linked.

[dalexeev]

Note: I did a check across the parser to see if any other of these would be missing and didn't find anything. I won't mind if someone else wants to double check.

I found one more:

godot/modules/gdscript/gdscript_parser.cpp

Lines 2148 to 2150 in 23318e8

	if (expression == nullptr) {
	push_error(R"(Expected expression for match pattern.)");
	return nullptr;

complete_extents(pattern);

[vnen]

Updated to include @dalexeev's find. Thanks!

[YuriSizov]

Thanks!

[YuriSizov]

Cherry-picked for 4.1.2.