[CORE] Fix race condition in AuthorizationRequestContext.loadRole()

[HarshMehta112]

Fixed #9084

• Replaced separate hasLoadRole.get() and hasLoadRole.set(true) calls with an atomic
  hasLoadRole.compareAndSet(false, true) operation.

• This makes the check-and-set atomic, ensuring the runnable executes only once,
  even under concurrent invocations.

• Previously, multiple threads could see false and execute the runnable simultaneously,
  causing duplicate executions.

• Added a new unit test: testLoadRoleRunsOnceEvenWhenInvokedConcurrently.

• Verified that the runnable executes only once, even when loadRole() is called concurrently.

Result

Improved thread-safety of loadRole() and prevented race conditions during concurrent access.

[justinmclean]

Please see the conversation in #9084. While this does fix the race condition it introduces some other issues and I think a little more needs to be done here.