Fix for variables losing scope and disappearing from debugger

[BigRed-118]

When breaking on or stepping to the last line of a p_block, the local
variables declared in that scope would be removed from the debugger.
This was because the current_line for removal set in gdscript_compiler.h,
pop_stack_identifiers ended up being the last line of the block, not
the line after. Now we set the current_line to be the end_line of the
p_block, only if the end_line is not -1

Reported: #38206

If anyone sees any issues with this let me know. From what I've seen, the end_line of a p_block was either a valid line or -1, but I could be mistaken. Thank you.

Bugsquad edit:

• Fixes Debugger loses variable scope in the last line of a block #53442

[BigRed-118]

The CF_xx block statements list doesn't end with a newline but with the last statement. Having the newline included might also be a solution for this, advancing to the next line at the end of the block, but I wasn't sure the impact it would have elsewhere.

[Banderi]

This was fixed in 4.0 which is what the master branch targets, correct?
Would it be fine if somebody remade this PR for the 3.x branch?

[akien-mga]

It would be good to do a new PR for 3.x yes.
Identifying what change fixed it in 4.0 could help inform whether the approach in this PR is correct, or if a better solution was found in 4.0 which would work on 3.x too.

[Banderi]

After a bit of narrowing down, this was the change that fixed it: #58201
Using the same approach, just changing this line from if (sd.line > p_line) { to if (sd.line >= p_line) { should do it - I'm gonna test if it works and open a PR for 3.x!

[akien-mga]

Superseded by #58201 (4.0) and #71093 (3.6).