Refactor the ImsiEncryption key download scenarios.

1. Retry the download in fail scenarios like device screen is locked or Internet is not avilable.
2. Do not delete the Key from the DB when a sim is disabled/removed where same operetor sim is active in another slot.
3. Optimize the logic not to execute on every carrierConfig change call.

Bug: 320955199
Test: Verified manually also atest tests/telephonytests/src/com/android/internal/telephony/CarrierKeyDownloadMgrTest.java
Change-Id: Ic77c8f923cda1728e81db9e64a15ca86b73d2069