Automated code coverage check for HarbourBridge

[manitgupta]

Currently we do not use the -cover mechanism in go test to generate coverage reports for HarbourBridge. In order to ensure incremental code coverage (velocity), we should create a CI/CD workflow which:

1. Generates code coverage report on each new commit to master or pull request.
2. Evaluates code coverage metrics and fails/passes the check based on statically configured criteria.

Code coverage criteria example - Reduction in % code coverage should be flagged.

[manitgupta]

We should also add a github badge to display the current code coverage of the package:

https://github.com/tj-actions/coverage-badge-go

We currently do this for the build status of the package.

[manitgupta]

Completed in #306.