Check if file exists instead of launching it

[DonJayamanne]

For #15725

[codecov-io]

Codecov Report

Merging #15726 (13775eb) into main (3ca66f9) will increase coverage by 0%.
The diff coverage is 50%.

@@          Coverage Diff           @@
##            main   #15726   +/-   ##
======================================
  Coverage     64%      64%           
======================================
  Files        557      557           
  Lines      26730    26725    -5     
  Branches    3887     3887           
======================================
- Hits       17292    17291    -1     
+ Misses      8708     8704    -4     
  Partials     730      730           

Impacted Files	Coverage Δ
src/client/common/configSettings.ts	69% <50%> (+<1%)	⬆️
src/client/providers/jediProxy.ts	23% <0%> (ø)
src/client/common/platform/fileSystem.ts	80% <0%> (ø)
src/client/common/installer/poetryInstaller.ts	95% <0%> (ø)
...nts/discovery/locators/services/condaEnvService.ts	80% <0%> (ø)
...discovery/locators/services/condaEnvFileService.ts	85% <0%> (ø)

[karrtikr]

Introduced #15782