[llvm] [llvm-cov][CoverageView] minor fix/improvement to HTML and text coverage output (PR #80952)

[Wentao Zhang via llvm-commits]

whentojump wrote:

> if you could backport this to the 18.x branch.

Yes I'm happy to.

I don't know the procedures well. To my preliminary understanding: first let's wait for this one to get merged into `main`; then I interact with `@llvmbot` here or somewhere else to do the backport. Is that right?


https://github.com/llvm/llvm-project/pull/80952