[automerger skipped] Keystore 2.0: Rename legacy_migrator to importer. am: 4a6ba6e8cd -s ours

am skip reason: Merged-In I0612d0731083548a196911712f6c0adbbc9a5e9a with SHA-1 0ffb8a80bd is already in history

Original change: https://googleplex-android-review.googlesource.com/c/platform/system/security/+/16909354

Change-Id: I9060a7ffa1a53f8c727136dd23bfb34e3788a1fe