Migrate to OsPath

We have a better alternative to FilePath now. See: https://hasufell.github.io/posts/2022-06-29-fixing-haskell-filepaths.html

What we should do:
1. Change `NormalizedFilePath` to `NormalizedOsPath` after the issue in lsp to support OsPath https://github.com/haskell/lsp/issues/445 is solved. Profiling it to make sure the performance improves.
2. Change other usages of `FilePath` to `OsPath`

However, this can not be done until `ghc-9.6` is released (ships the new `filepath` library), or all ghc shipped libraries are available on Hackage.
> Many GHC bundled libraries do not have new versions released to Hackage (for example ghci and hpc, their versions on hackage is very old). Thus, cabal solver fails if I add filepath ^>= 1.4.100.0 to a project that depends on ghc, which then depends on ghci. The installed ghci links against filepath-1.4.2.2 in this case, and cabal can not rebuild a ghci with filepath ^>= 1.4.100.0, as the source code is not found on hackage.