set subscription-admin cluster role to be the managedclusterset admin

[xiangjingli]

• I have taken backward compatibility into consideration.

https://issues.redhat.com/browse/ACM-7147

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (main@d1fd79e). Click here to learn what that means.
Patch has no changes to coverable lines.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #363   +/-   ##
=======================================
  Coverage        ?   54.54%           
=======================================
  Files           ?       71           
  Lines           ?    14948           
  Branches        ?        0           
=======================================
  Hits            ?     8153           
  Misses          ?     5971           
  Partials        ?      824           

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unit	54.54% <ø> (?)

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[openshift-ci]

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