The ResourceLoader classes will be moved to the MediaWiki\ResourceLoader namespace.
All class names will have the "ResourceLoader" prefix removed from them except ResourceLoader and ResourceLoaderContext.
I am introducing a convention where the namespace is imported with the alias RL, so that you have e.g. RL\Module as the new name for ResourceLoaderModule instead of just Module.
There is a bug in Phan which causes a spurious PhanParamSignatureRealMismatchParamType error on classes using the old \ResourceLoaderContext type on parameter type declarations for classes extending ResourceLoaderModule, only if the target PHP version is less than 7.4 (T308443). To work around this, either simultaneously update the affected extension, or to add @phan-suppress PhanParamSignatureRealMismatchParamType to the doc comment.