Add Python unit test coverage report

[bstefanuk]

Objectives:

• Add unit test coverage reporting for Tensile's Python applications.
• Refactor the location in CI where unit tests are being invoked.
• Clarify boundaries between tests of different types both in CI and in tox.ini
• Move towards standardized function definitions in groovy files

Outcomes:

• Unit tests are now run in the testing stage of the pipelines instead of the compile stage.
• Changes to testing environments available via tox run -e <ENV>
• Refactored dependencies and structure of tox.ini
• Removed unused lines of code in groovy bash commands.

Notable changes:

• JUnit reports are no longer created and saved in CI. This shadows other ROCm libraries which are removing JUnit because of it increases job times and provides redundant reports that are otherwise reported in the job logs.
• No more fallback testing environments; the user must be explicit about what they want to be run.
• Generic testing environment is renamed to ci instead of the previously used fallback commands.
• Changed skip*Test flag in groovy functions to run*Test and inverted conditionals.