[FR]: Support lcov parsing for coverage

### What is the current behavior?

Part of https://github.com/bazelbuild/bazel/discussions/19144 - bazel's coverage support only produces the LCOV format, and expects users to install some other tool like `genhtml` to view the result.

### Describe the feature

Aspect CLI could include an lcov parser and be able to produce more useful outputs like cobertura XML, and it could also print a coverage summary itself.

Another use-case: this GHA is slow https://github.com/aspect-build/rules_py/actions/runs/12920978802/job/36034199684 because it uses hrishikesh-kadam/setup-lcov@6c1aa0cc9e1c02f9f58f01ac599f1064ccc83470 to install some packages, just to print a coverage summary.

No files or tests are named. Start by locating the Aspect CLI's existing coverage-related entry points and reviewing the LCOV, Cobertura XML, and summary requirements described here. Done means the CLI can parse LCOV and produce the requested useful outputs without requiring an external coverage tool.

Written by the indexing model from the issue text.