LDrawLoader: Refactor, cache pre-parsed file contents (#23157)

* this.cache -> this.fileCache

* Add in parsed data cache

* small fixes

* material fixes

* Remove FileCache

* Use in order materials from the local scope if possible

* simplify fetchData, ensure fetch errors are caught, throw a real error

* clone result, material simplification

* improve clone result perf

* Fix colors

* simplify cache API

Author: gkjohnson