Lwc: [engine] refactor unit tests into karma integration tests

[ekashida]

Many of our unit tests are sensitive to compiler changes because they rely on non-public APIs. They should be refactored to only use public APIs.

[ekashida]

@ravijayaramappa can you confirm this is no longer the case?

[ekashida]

Discussed with @ravijayaramappa and we agreed this should stay open until we refactor all tests that use compileTemplate.

[git2gus[bot]]

This issue has been linked to a new work item: W-7273573

[ravijayaramappa]

We no longer have tests that use compileTemplate.