move fstat to libphoenix

[lukileczo]

JIRA: RTOS-790, RTOS-791

Description

• save unix socket oid in open_file_t structure after binding
• remove fstat
• add fdResolve syscall to resolve fd -> oid

Motivation and Context

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [x] Breaking change (fix or feature that would cause existing functionality to change)

How Has This Been Tested?

• [x] Already covered by automatic testing.
• [ ] New test added: (add PR link here).
• [ ] Tested by hand on: (list targets here).

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [x] All new and existing linter checks and tests passed.
• [x] My changes generate no new compilation warnings for any of the targets.

Special treatment

• [x] This PR needs additional PRs to work https://github.com/phoenix-rtos/libphoenix/pull/352
• [ ] I will merge this PR by myself when appropriate.

[nalajcie]

Additional issues to consider:

• INET sockets fstat needs to be handled by lwip (not done now)
• UNIX socket port == -1, maybe we need to create another in-kernel server for unix sockets?
• PIPEs also need extra support in posixsrv now?