Internal: Add caching to improve the Def ID to AST pointer lookup.

[Kohei316]

Close: #17116

This PR include these changes.

• Implement a cache that maps Def ID to Ast Ptr.
• Modify to use optionally the cache when searching for sources in hir-def crate.
• Modify Semantics to possess the cache.
• Modify to use the cache through Semantics when searching for sources in hir crate.

[Veykril]

Implement a cache that maps Def ID to Ast Ptr.

Hmm, this seems a bit unnecessary to me. The main idea behind that issue was to cache the parse trees / avoid the LRU cache on the parse query when possible, not the DefId -> AstPtr direction

[bors]

:umbrella: The latest upstream changes (presumably #18022) made this pull request unmergeable. Please resolve the merge conflicts.

[Veykril]

Closing due to inactivity