Editor: Improve signal callback generation

[dalexeev]

Note: Some changes have been extracted to #80745, #80765 and #81079.

Added support for typed arrays, enums and Variant.

[raulsntos]

The C# changes look good to me. Should likely be reviewed by the Editor team as well.

[YuriSizov]

This looks like an improvement, and a bugfix too. There are probably still cases which aren't handled perfectly, but they are certainly not handled worse than before.

[akien-mga]

Thanks!