Stabilize environment extension API

[karrtikr]

Currently blocked on Jupyter feedback: microsoft/vscode-jupyter#7583.

General feedback issue: #18888

[karrtikr]

Waiting on microsoft/vscode-jupyter#7583 (comment) to decide whether to finalize this in the next iteration.

[karrtikr]

Make sure to also finalize #20056 along with this issue, and deprecate existing related stable APIs.

[karrtikr]

• getActiveEnvironmentPath & resolveEnvironment fails to return the active environment information  #20147
• Environment Id is not static (it changes) when installing Python into an empty Conda environment #20176
• Slow environments.known #20221
• Clear documentation on the arguments for resolveEnvironment #20220
• Python API triggers add events even after refresh promise has resolved #20216

[karrtikr]

List of all issues: #20240.

[karrtikr]

@DonJayamanne As things look good with Jupyter we plan to finalize this API in this iteration, just an FYI.

[DonJayamanne]

FYI - Its possible (depends on the solution/change) there could be some API changes as a result of this #20765

[karrtikr]

Verification steps:

See https://github.com/microsoft/vscode-python/wiki/Python-Environment-APIs#extension-api-usage for usage examples, choose any one example and ensure API still works.

[DonJayamanne]

Works well, as expected.

@karrtikr Should we have a sample extension for this, else verification is time consuming, and any changes made would require repeating the same time consuming effort

[karrtikr]

Sounds reasonable, will add it in the example wiki sent earlier.