WIP (very wip) Index macro expansions

[vlad20012]

Now most macros are expanded once (together with indexing) and stored persistently. This opens the way to index macro expansions, and thus support impls/modules declared with macros, and also make auto-import, find symbol/usages (and other index-driven features) to work with macros.

Also it should significantly increases performance.

Closes #2458.
Also fixes #2615, fixes #2902, fixes #2787, fixes #3006, fixes #2383, fixes #955, fixes #3087, fixes #3259, (... and more)

TODO:

• support macro call insertion (bug)
• replace java-serialization with something more meaningful
• compress expansion-file urls
• fix spawning tons of background tasks
• use write-priority retryable read actions
• support modules defined with a macro (improve module index)
• split expansion task into several batches (?)
• validate expanded macros sequentially (don't re-expand macros that may be invalidated by other expansions in same task)
• disable inspections/annotators while expanding macros
• think about project root / search scopes
• re-validate only workspace macros on local change
• clear dangling expansions (check consistency) on startup
• fix expansion of not-item macros
• fix performance tests
• add completion tests
• clear macros directory if not accessed for a long time