[FR]: Support lcov parsing for coverage

[alexeagle]

What is the current behavior?

Part of bazelbuild/bazel#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@6c1aa0c to install some packages, just to print a coverage summary.