LSP: Fix spec violations that break the VSCode outline

[HolonProduction]

Fixes #98164

This contains fixes to two situations that would break the vscode outline:

1. The one described in [LSP] Scripts doesn't begin with extends in the first line shows 'can't find symbols' in the outline #98164:
   As noticed in the issue: with the comment on the first line, the range of the root symbol shifts, which is fine. However, the spec for selectionRange requires the selection range to be inside of the range. When the class has no class_name we would just leave the selection range on its default of the start of the first line. With the root symbol shift this means, that the selection range is outside the range which is a spec violation and breaks the VSCode outline.

Figuring this out was so much more work than the three line fix would make it seem TwT

2. The conversion between GDScript positions and LSP positions did not take a special case into account where the GDScript column is set to 0 but the line is set 1, for this case it would output an invalid lsp column value of -1 which would break the VSCode outline as well. This case can happen in scripts without extends and class_name statements.

[akien-mga]

I'm not familiar with the LSP so I'll trust you that this is the correct fix. I assume it was tested on VS Code.

Might be worth testing on e.g. neovim which I believe also has a GDScript LSP implementation. https://github.com/niscolas/nvim-godot

[limbonaut]

I've tested this PR with the limbonaut/limboai#194 issue and Code OSS.
It works well! 😊