feat: subordinate protocol validation and deletion check

[janiussyafiq]

Description

Which issue(s) this PR fixes:

Fixes #6939
This PR implements subordinate (parent–child) relationship validation for stream routes in the Admin API, as proposed in issue #6939. Previously, stream routes could reference a superior_id without any validation, which could lead to invalid configurations, broken dependencies, and runtime routing errors.

This change ensures that:
• Any referenced superior stream route must exist.
• The protocols between subordinate and superior routes must match.
• A superior stream route cannot be deleted if it is still referenced by another route.

Also added some test cases for this update.

Checklist

• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the APISIX mailing list first)

[Baoyuantop]

Duplicate of #12794

[Baoyuantop]

Hi @janiussyafiq, since PR #12794 has already implemented the same changes, this pull request has been closed. Thank you for your contribution.