!syscall: Change sys_unlink/link API to allow pointer checking

[agkaminski]

JIRA: RTOS-939

Description

Motivation and Context

Fixes phoenix-rtos/phoenix-rtos-project#976

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Chore (refactoring, style fixes, git/CI config, submodule management, no code logic changes)

How Has This Been Tested?

• Already covered by automatic testing ([DO NOT MERGE} RTOS-939 test phoenix-rtos-project#1196)
• 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.
• All new and existing linter checks and tests passed.
• My changes generate no new compilation warnings for any of the targets.

Special treatment

• This PR needs additional PRs to work (!file: Pass pathlen in sys_unlink/link, adapt to the kernel API change libphoenix#385).
• I will merge this PR by myself when appropriate.

[github-actions]

Unit Test Results

7 168 tests   - 557   6 477 ✅  - 533   40m 41s ⏱️ + 1m 53s
  445 suites ±  0     667 💤  -  48 
    1 files   ±  0      24 ❌ + 24 

For more details on these failures, see this check.

Results for commit b9e7449. ± Comparison against base commit d99dc74.

This pull request removes 561 and adds 4 tests. Note that renamed tests count towards both.

phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype._tolower
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype._toupper
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isalnum
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isalpha
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isascii
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isblank
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.iscntrl
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isdigit
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.isgraph
phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc.ctype.islower
…

phoenix-rtos-tests/libc/misc ‑ armv7a7-imx6ull-evk:phoenix-rtos-tests/libc/misc
phoenix-rtos-tests/libc/misc ‑ armv7a9-zynq7000-qemu:phoenix-rtos-tests/libc/misc
phoenix-rtos-tests/libc/misc ‑ armv7a9-zynq7000-zedboard:phoenix-rtos-tests/libc/misc
phoenix-rtos-tests/libc/misc ‑ ia32-generic-qemu:phoenix-rtos-tests/libc/misc