Add Github Actions to lint, test and produce code coverage

[ddl-ebrown]

• When run in CI, the coverage dir is missing for some reason, so
  gotestsum won't run properly

• Emit junit output from make test-coverage

• Since we don't yet have SDLC pipeline projects for Go libraries or
  for public projects, add in some limited CI validation for PRs to
  this repo including:

  • A build and test stage that generates binaries with the Makefile
    and runs make test-coverage to produce coverage (not currently
    used in CI)

    Also uploads these as artifacts

  • Linting through the golangci-lint Github Action

• NOTE: intially use dorny/test-reporter which produces Github checks,
  which by design doesn't always attach to the right workflow - results
  may show up with golangci-lint. See

  Test report doesn't appear in expected place in GitHub UI dorny/test-reporter#67
  https://github.com/orgs/community/discussions/24616

  To resolve this, switch to a fork that uses summary instead:
  feat: add output to step summary phoenix-actions/test-reporting#21

• Building on the prior CI changes to lint and produce test artifacts,
  use the action go-coverage-report to examine the cover.out file
  produced to generate a small coverage report

[ddl-ebrown]

Code coverage won't work until at least one run has been merged