Code coverage is outdated and not being used

[simonrouse9461]

Currently we are using actions-rs/grcov for generating code coverage report. However, it's been failing for a long time.

Root causes:

• Latest builds require a newer version rust toolchain (>= 1.82), which is not compatible with actions-rs/grcov.
• actions-rs/grcov has been marked as archived.
  • actions-rs/grcov relies on -Zprofile flag from old nightly rust toolchain.
  • In newer versions of rust, -Zprofile has been removed

We can use alternative ways to generate coverage reports, but as suggested by @alancai98, it's not actually needed for this repo at the moment as we are not running any test cases.

Solution: @alancai98 suggests that we should just remove coverage.yml along with codecov.yml. We can add them back once needed.