chore: remove fleet v1alpha1 internal member cluster controller

[weng271190436]

What type of PR is this?

/kind cleanup

Optionally add one or more of the following kinds if applicable:
/kind deprecation

What this PR does / why we need it:

Which issue(s) this PR fixes:

Remove fleet v1alpha1 API

Fixes #

Requirements:

• run make reviewable for basic local test
• Read and followed fleet-networking's Code of conduct.
• uses conventional commit messages
• includes documentation
• adds unit tests

How has this code been tested

Special notes for your reviewer

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[weng271190436]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 67.42%. Comparing base (677dc3b) to head (a08d206).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #343      +/-   ##
==========================================
+ Coverage   67.31%   67.42%   +0.11%     
==========================================
  Files          34       33       -1     
  Lines        5060     4884     -176     
==========================================
- Hits         3406     3293     -113     
+ Misses       1465     1413      -52     
+ Partials      189      178      -11     

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