Split CI tests into seprate jobs (temporary work around for flaky tests)

[DonJayamanne]

Split CI tests into three separate jobs:

• Debugger tests
• Single workspace tests
• Multiroot workspace test

Purpose:

• Faster tests on CI
• Easier to restart a specific test (rather than running all test all over again)

Currently the above three sets of tests are already run separately. Running them as separate jobs on CI will make it easier to re-start one of them without having to re-run everything all over again.

Temporary work around until we get flaky tests running properly
This could lay the ground works for running Integration tests on a release branch

• Known (flaky test - experimental debugger) Experimental debugger fails to stop at breakpoint on CI server (multi-threaded code) #1250