Enhancement : Move coverage to the test extract

[conveyanand]

Is your feature request related to a problem? Please describe.
coverage dependency is listed under runtime dependencies in pyproject.toml, which is not needed by normal library users in general.
Installing PyPulseq currently includes test tooling that only belongs in the test environment.

Describe the solution you'd like
Move coverage from [project].dependencies to [project.optional-dependencies].test.
Keep runtime dependencies limited to packages needed when importing and using PyPulseq.

Describe alternatives you've considered
Leave coverage in runtime dependencies for convenience, but that keeps unnecessary test tooling in normal library installs.

Additional context
None to report

[btasdelen]

Agreed. Can be handled together with #393.

[conveyanand]

Yes, we can address it as part of #393 but don't see any changes or references in #396 yet. I guess this will be taken care !