Currently the performance selection of interpreters is left at the mercy of external tools such as conda and the like. On Windows these tools can be extremely slow.
This will only get slower as we support more sources for interpreters or if conda and other tools get slower).

Suggestion:

• Cache list of interpreters (filter to exclude invalid items, easy file check)
• Cache list of conda environments (re-query only if we have new items in environments.txt)
• Display partial list of interpreters while conda and the like run in background
• Display Loading Conda Envs in list for those not yet completed (could apply to registry searches as well)

This should improve ux significantly (at least in Windows).