Coverage calculation for C++ and Rust

Currently issues with coverage calculation are observed across different Modules. We need a common solution that can be applied and used in reference_integration.

Problem definition

Mutual

• we need solution that is common and can be reused by everyone
• we need justifications when coverage != 100%, we need mechanisms to justify etc.
• tooling should support platform variants, allows justifications only for specific one, etc.
• tooling should allow easy use to developers and clear information where improvements are needed
• tooling will require certification but there is no other known alternative that will fulfill all our requirements
• tool requirements initially defined in https://github.com/eclipse-score/communication/pull/549

C++

• different frameworks have different statements definition - we need that aligned in SCORE
• bazel coverage is not 100% reliable
• PR with suggested changes as reference https://github.com/eclipse-score/communication/pull/549
• No other alternatives exist for our knowledge right now

Rust

• currently only line coverage is calculated
• ferrocene toolchain supports only Linux (QNX UTs don't work)
• there was a new PR in toolchains to support coverage in QNX @PiotrKorkus to check if that works
  https://github.com/eclipse-score/bazel_cpp_toolchains/pull/62
• other coverages where quoted to ferrocene. Branch coverage would be possible to get with other open-source solutions

It should be possible to use a common tool for generating coverage for both languages.

Next steps

• Get QNX coverage working for C++
• Look into Rust coverage
• Rust and C++ report should have a combined report