coverage: return InstrumentedFilesInfo from haskell_library/binary/test

[briantopping]

Problem

rules_haskell ships HPC coverage, but its rule implementations never return Bazel's InstrumentedFilesInfo. Without it, bazel coverage can't deterministically instrument the transitive Haskell libraries in a test's closure: a library is realized in both instrumented and non-instrumented configurations within one coverage //... run, and a test linking the non-instrumented variant produces no <lib>_.hpc — so its covered modules silently score 0%.

Fix

Return coverage_common.instrumented_files_info at the provider sites:

• _haskell_binary_common_impl (haskell_binary + haskell_test): source_attributes = ["srcs"], dependency_attributes = ["deps", "narrowed_deps"].
• haskell_library_impl: dependency_attributes additionally includes "exports".

haskell_library_impl is reused by haskell_proto_aspect via a patched-ctx struct (the existing real_ctx indirection), which isn't a genuine rule ctx and which coverage_common.instrumented_files_info rejects — so the provider is attached only for a real rule ctx (no real_ctx attribute), preserving the aspect's provider contract.

Why upstream

Generic coverage-correctness fix, nothing project-specific — any user running bazel coverage over a multi-library Haskell target gets non-deterministic transitive-library coverage today.

Verification

buildifier clean; cherry-picks cleanly onto current master. Carried in a downstream fork where it makes HPC→lcov scoring deterministic. Not yet exercised with a fresh bazel coverage on master here — happy to confirm if a maintainer prefers.

[avdv]

Thank you!

Does this have any effect on the tests in rules_haskell_tests, e.g. the two-libs one ?