ide_db: build symbol index from crate def map

[jhgg]

fixes #4842, #10764

Is this looking correct? 👀

• build the symbol index based upon the CrateDefMap for the given crate in crate_symbols
  • make it multi threaded again, and figure out how to cache each moduleid's symbol index in salsa.
  • NavigationTarget for names in macros is wrong, need to figure out how to compute a text range in the original file id?
  • cleanup some duped code
  • collect macros from ItemScope.declared_macros() into symbol index.
    • store declared macros in ItemScope so we can figure out where macros were defined for the index.
  • do something about SymbolIndex::for_files - ideally it should use the new module symbol index stuff.
    • delete source_file_to_file_symbols & co...
      • figure out what to do about library_symbols
      • maybe... speed up the new library_symbols - the new impl is probably much slower, and definitely much less parallel. deciding to do nothing here, we can optimize later if necerssary.
  • fix failing test: navigation_target::tests::test_nav_for_symbol - notably the crate def map doesn't seem to find declarations inside function.
    • now a bunch of other tests are failing around auto_import & qualify_path handlers. :(
      • need to assoc items in traits and impls

[jhgg]

some questions:

1. it looks like library_symbols is a bit bespoke, insofar as it operates directly on re-parsed source text. is there a specific reason for this? would changing it to use a def map be problematic?

   • it looks like library_symbols additionally does not seem to have a way to access RootDatabase? if not, what would be the advisable strategy to parallelize. (i figure i need a RootDatabase to do a snapshot to distribute to worker threads)

2. the new def map based symbol index does not descend into function bodies to find symbols, this has caused a test to fail. any tips on how to resolve? 8850ea0

[Veykril]

bors r+

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)