Factor out path-related classes for better testing.

[ericsnowcurrently]

(for #8995)

This adds back in some of the refactored code and high-level functional tests reverted in #8970. It also adds more tests and gets things ready for #8542 (where we will drop the pathutils module, etc.).

[codecov-io]

Codecov Report

Merging #9352 into master will increase coverage by 0.02%.
The diff coverage is 67.9%.

@@            Coverage Diff             @@
##           master    #9352      +/-   ##
==========================================
+ Coverage   60.93%   60.95%   +0.02%     
==========================================
  Files         529      530       +1     
  Lines       28580    28632      +52     
  Branches     4339     4338       -1     
==========================================
+ Hits        17415    17454      +39     
- Misses      10214    10227      +13     
  Partials      951      951

Impacted Files	Coverage Δ
src/client/common/types.ts	100% <ø> (ø)	⬆️
src/client/common/platform/constants.ts	100% <ø> (ø)	⬆️
src/client/common/platform/types.ts	100% <100%> (ø)	⬆️
src/client/common/platform/pathUtils.ts	61.9% <53.84%> (+1.03%)	⬆️
src/client/common/platform/fileSystem.ts	26.87% <60%> (-0.57%)	⬇️
src/client/common/platform/fs-paths.ts	71.92% <71.92%> (ø)

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[karrtikr]

Can you please also manually run CI against this PR?

[ericsnowcurrently]

@karrtikr Will do. What motivated you to ask? (it's not a normal step)

[DonJayamanne]

Your previous PR broke master when merged. When making large changes I'd recommend running CI against a PR.
It's not because you've done anything wrong, just that the functional tests are more extensive and thin on CI (as they are slow they dont run on PR pipelines)...

[ericsnowcurrently]

Agreed. The failing functional tests are tests that I added. 😄 I just hadn't run them on Windows and apparently that did not happen during PR validation. (and FWIW, the change wasn't that large; most of it was tests)

[karrtikr]

If the CI has no failing tests for this PR, feel free to merge it.

[ericsnowcurrently]

I'm pretty sure those 2 failures are not due to this PR. I'll double-check tomorrow before merging.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

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

No Coverage information
0.0% Duplication

[ericsnowcurrently]

Yep, the Windows tests have been timing out on master and the OSX tests all passed when I re-ran CI.