Replace 'iox::string' with semantically appropriate types like `FilePath`

## Brief feature description

In many places an `iox::string` is used instead of a semantically more appropriate type like `FilePath`. In order to prevent superfluous checks and easy to make mistakes the semantically appropriate type shall be used.

See also https://github.com/eclipse-iceoryx/iceoryx/pull/2016#discussion_r1315024006

## Detailed information

Tasks

- [ ] Check the usage of `iox::string` in the API
- [ ] Replace `iox::string` with `FileName`, `UserName`, `GroupName`, `FilePath` and `Path`
- [ ] Use `FileName` for `RuntineName_t`, which is an `iox::string` alias
- [ ] Use `FileName` for `detail::PosixSharedMemory::Name_t`, which is an `iox::string` alias