Move getLastKnownCellIdentity to its own flag.

Moving this API to a different flag so that it won't block 24Q3; it will
launch is 25Q3.

Test: This API has a CTS test.
Bug: 327454165
Change-Id: Ibc844d9a3300a75cf3b852f10aa0e0fcc92039f9
1 file changed