Expose currently selected interpreter path using API

[karrtikr]

For #11294

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR).
• Title summarizes what is changing.
• Has a news entry file (remember to thank yourself!).
• Appropriate comments and documentation strings in the code.
• Has sufficient logging.
• Has telemetry for enhancements.
• Unit tests & system/integration tests are added/updated.
• Test plan is updated as appropriate.
• package-lock.json has been regenerated by running npm install (if dependencies have changed).
• The wiki is updated with any design decisions/details.

[karrtikr]

Blocked on the email thread where we're finalizing the design.

[karrtikr]

Please re-review @int19h @kimadeline

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
0.0% Duplication

[codecov-io]

Codecov Report

Merging #11295 into master will decrease coverage by 0.08%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #11295      +/-   ##
==========================================
- Coverage   61.12%   61.03%   -0.09%     
==========================================
  Files         602      604       +2     
  Lines       33147    33421     +274     
  Branches     4685     4732      +47     
==========================================
+ Hits        20260    20400     +140     
- Misses      11866    11995     +129     
- Partials     1021     1026       +5     

Impacted Files	Coverage Δ
src/client/common/configSettings.ts	70.39% <ø> (ø)
src/datascience-ui/react-common/arePathsSame.ts	75.00% <0.00%> (-12.50%)	⬇️
src/client/common/utils/platform.ts	64.70% <0.00%> (-11.77%)	⬇️
src/client/linters/pydocstyle.ts	86.66% <0.00%> (-2.23%)	⬇️
src/client/datascience/debugLocationTracker.ts	76.56% <0.00%> (-1.57%)	⬇️
...lient/datascience/jupyter/jupyterSessionManager.ts	7.07% <0.00%> (-1.11%)	⬇️
src/client/common/process/proc.ts	14.49% <0.00%> (-0.73%)	⬇️
...ascience/jupyter/liveshare/guestJupyterNotebook.ts	9.62% <0.00%> (-0.67%)	⬇️
...pplication/diagnostics/checks/pythonInterpreter.ts	91.07% <0.00%> (-0.60%)	⬇️
src/client/common/types.ts	100.00% <0.00%> (ø)
... and 23 more

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