Improve PR validation Azure DevOps pipeline process.

[d3r3kk]

For #4123

(Also for #3898, #4034, #4648, perhaps others)

• Add Python Pytest build phase to each OS Azdo CI to run python tests #4034, Run extension python tests on Python 2.7 #4648
• Capture JUnit logfile from Pytest test runs Azdo CI to run python tests #4034
• * Remove test jobs from this build to ensure faster turnaround.
  • remove them only from Windows, where they are failing at the moment due to timeouts. Faster Azure CI Pipelines #3898
  • testSingleWorkspace removed from Windows builds.
  • testMultiworkspace, testDebugger removed from all builds. Faster Azure CI Pipelines #3898
  • venvTests removed from all builds
• The build-then-test hierarchy I originally devised can be removed. Consider reducing/moving Azdo jobs from PR to nightly CI #4123
  • No upload/download steps on the PR validation build. Consider reducing/moving Azdo jobs from PR to nightly CI #4123
• Don't install test requirements for Python until & unless absolutely necessary. (this is the slowest dependency we have). Consider reducing/moving Azdo jobs from PR to nightly CI #4123
• Don't build the vsix Consider reducing/moving Azdo jobs from PR to nightly CI #4123
• Add the missing test phases we have in Travis to AzDO here.
• Windows will get a smaller timeout for the big tests (30 min) and will be allowed to fail.
• Each task should be documented to describe what it does in detail.
• Each task should represent one or two command-line operations that we can replicate on our local machines.

Note: There will be a follow-up PR that will make the steps used inline in this process shared between PR + CI builds.

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• [no] 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!)
• 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.

[rchiodo]

🕐

[rchiodo]