Update Assets fields on project build

[RblSb]

Keep Assets.type fields cache with mtime (modification time) and invalidate them when files.json modification time is updated. Also keep files.json cache/mtime.

Before this change: after you add new image, you need to build project and then restart haxe language server to fix missing field errors.
With this change: after you add new image, you only need to build project to update fields in Assets.

Tested with haxe4/haxe5.

I also added same cache impl to ShadersBuilder, because in Haxe 5, after registerModuleDependency and files.json update, macro will reparse files.json on every file focus (HaxeFoundation/haxe#12846).

I used this cache impl as reference: https://github.com/HeapsIO/heaps/blob/72143b6c4c72a8895d713b5d850258cac53ff4bf/hxd/res/DynamicText.hx#L366

There is also basic debug mode with reparse/invalidation traces when they happen, i can remove it.

[RobDangerous]

Groovy!