Revert of the v9.0 backport of SERVER-125964 on the v9.0-staging branch.

Reverts v9.0 commit cd110561e349768aee3bef089ad5f4d12646f55b ("SERVER-125964: Apply initial sync oplog entries from initiating set oplog entry if the set recently initiated (#53949)").

This mirrors the revert already landed on master as PR #61207 (6d8c74047666). SERVER-125964 is a sub-task of SERVER-113184, whose initial sync changes have been backed out of master; the v9.0 branch is being brought back in line.

Removes the initiating-set oplog application logic from initial_syncer.cpp/.h and initial_sync_state.h, the initialSyncWaitForSyncSourceLastStableRecoveryTs and related server parameters from repl_server_parameters.idl, the associated unit tests and jstests, and the corresponding etc/backports_required_for_multiversion_tests.yml entries.

Note: jstests/replsets/initial_sync_check_initiating_set_oplog_entry.js, added by this backport, is deleted in the SERVER-127512 revert commit on the branch rather than here.