* we can now read preflight specs out of secrets, either from stdin or file input
* moved spec read logic out into its own function so it can be unit
tested easier
* added more comprehensive unit testing on the different ways we can read in specs
* adding test coverage for preflight.RunPreflights()
TDD to work on https://github.com/replicatedhq/troubleshoot/issues/906
and verify the fix is successful
* go.mod/go.sum: removing gnomock stuff since it's not in use (yet)
* Makefile: try running the preflight integration test with the e2e tests,
since there's a K3s instance in place already
* Makefile add a dedicated test-integration task, which runs as it's own
github action job
* Makefile: exclude a few things from test-integration that break the
github action job
* WIP on preflight tests, addressing some of @banjoh's feedback, more to
go though (specifically changing over to using assert)
* preflight tests: use the testify libraries, restructure code to be
formatted more like other tests in this project
