[clang] [clang][deps] Simplify by-module-name scan API (PR #184376)

[Kewen Meng via cfe-commits]

Kewen12 wrote:

Hello! It seems this PR breaks our buildbot with old GCC. Would appreciate if you could take a look. Thanks!

bot: https://lab.llvm.org/buildbot/#/builders/140/builds/39953

```
/home/botworker/bbot/builds/openmp-offload-sles-build/llvm.src/clang/lib/Tooling/DependencyScanningTool.cpp:353:10: error: could not convert ‘CIWithContext’ from ‘clang::tooling::CompilerInstanceWithContext’ to ‘std::optional<clang::tooling::CompilerInstanceWithContext>’
   return CIWithContext;
```

https://github.com/llvm/llvm-project/pull/184376