Spike: Investigate using webworker for Python discovery

[karrtikr]

#15813

[karrtikr]

Spike

Discovery = locator + watcher + resolver

vscode module is not available to use in worker threads, so we have to refactor them out. APIs we currently use:

• Locator requires workspace.workspaceFolders and workspace.onDidChangeWorkspaceFolders
• Watcher requires workspace.createFileSystemWatcher, EventEmitter, RelativePattern
• Uri itself
• ...maybe more

Resolver & locator part are expensive, watcher can be outside. The issue right now is watcher is part of the locator, locator gives out existing environment locations and watcher returns whether there's an new env in those locations.

[karrtikr]

Spawning conda or "REG" binary (windows registry) can block the main thread for a few seconds:

[karrtikr]

Perf analysis of where time is spent on extension load, and how discovery impacts it:

• discovery_fresh_startup.cpuprofile.txt
• ls_with_discovery.cpuprofile.txt
• ls_with_discovery_partial_proposal.cpuprofile.txt
• ls_with_discovery_proposal.cpuprofile.txt
• ls_without_discovery.cpuprofile.txt

[karrtikr]

Spike results: #22146 (comment)