Auto import memory optimizations

[andrewbranch]

• Deduplicates package extraction work and *autoimport.Export and entrypoint info objects by realpath, which can be significant when many workspace packages have the same dependencies and resolve them via symlink (thanks @goloveychuk for noticing this)
• Replaces a collections.Set[string] on each Export with bitflags
• Pulls in Share package.json cache and skip collecting failed lookup locations in auto-imports #2855

Should help #2780

Results

Measured by opening one file in each workspace package and triggering auto-imports.

repo-pnpm - 10 packages

	/gc/heap/live:bytes
nightly	1,245,135,800
pr	753,368,456

vscode - 1 package

	/gc/heap/live:bytes
nightly	1,590,839,104
pr	1,089,793,528

DefinitelyTyped-tools - 14 packages

	/gc/heap/live:bytes
nightly	476,638,976
pr	368,886,320

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[jakebailey]

Totally not for this PR, but for the language server, I wonder if we should just say "GetSourceFile must always returns a bound file" given we largely assume that to be the case.

[goloveychuk]

(It's found by ai. With my idea/assumption though)