AS-542: Use gh actions for unit tests [risk: low]

[davidangb]

Use GH Actions for unit tests instead of Travis.

Because the GH Actions -> Coveralls integration for sbt is weak (see for instance https://github.com/lemurheavy/coveralls-public, issue 1388), this PR also:

• switches from scoverage to sbt/sbt-jacoco to generate coverage reports
• switches from coveralls to codecov as our hosted coverage service

Note that the Travis checks for this PR will fail, because I've removed the .travis.yml; this is expected until we disable Travis for this repo. Once this PR is approved, I'll change which checks are required for PRs.

---

Have you read CONTRIBUTING.md lately? If not, do that first.

I, the developer opening this PR, do solemnly pinky swear that:

• I've followed the instructions if I've made any changes to the API, especially if they're breaking changes
• I've updated the RC_XXX release ticket with any manual steps required to release this change
• I've updated the FISMA documentation if I've made any security-related changes, including auth, encryption, or auditing

In all cases:

• Get two thumbsworth of review and PO signoff if necessary
• Verify all tests go green
• Squash and merge; you can delete your branch after this unless it's for a hotfix. In that case, don't delete it!
• Test this change deployed correctly and works on dev environment after deployment

[coveralls]

Coverage remained the same at 64.359% when pulling 362a41e on da_unitTestActions into 080afb6 on develop.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (develop@080afb6). Click here to learn what that means.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             develop    #818   +/-   ##
=========================================
  Coverage           ?   0.00%           
=========================================
  Files              ?     115           
  Lines              ?    3263           
  Branches           ?     510           
=========================================
  Hits               ?       0           
  Misses             ?    3263           
  Partials           ?       0           

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[ansingh7115]

it's nice we don't need these steps anymore!

[ansingh7115]

Will the "Missing base commit" error be automatically fixed when this is merged - is it just because this is the first time we're using it that we're getting this error?

[ansingh7115]

Looks like the tests run as they should on GitHub Actions

[davidangb]

@ansingh7115 yup, I expect that the "missing base commit" error from codecov will be fixed after this merges and we start to upload ongoing coverage reports to them. If it remains a problem, we'll fix it!