GenerateWindowOrWorkerInterfaces
`lexical_bases` was storing `StringView`s into `ByteString`s returned from `LexicalPath::string()` that might no longer exist.
This will allow the CSSStyleDeclaration IDL attribute generator to implement it's own C++ acceptable identifier sanitization and deduplication.
This allows us to specify multiple base paths to look for imported IDL files in. This will allow us to import IDL files from sources and from the Build directory (i.e. for generated IDL files).