- Report a diagnostic when there are multiple classes that match the script file name in the same script since that will result in a duplicate path key in the bimap and it's not allowed.
- Fix InspectorPlugin to handle empty paths in case the project was built with a previous version of Godot that used empty paths for generic scripts.
- Add tests for the new diagnostic GD0003.
The editor no longer needs to create temporary instances to get the
default values. The initializer values of the exported properties are
still evaluated at runtime. For example, in the following example,
`GetInitialValue()` will be called when first looks for default values:
```
[Export] int MyValue = GetInitialValue();
```
Exporting fields with a non-supported type now results in a compiler
error rather than a runtime error when the script is used.
