Provide a machanism to override MVNO parameters below CarrierConfig

- maintain fake variables of imsi, gid1, gid2, and spn in IccRecord,
and add them into toString() and dump()
- provide a machanism to override Imsi, gid1, gid2, and spn during
sim/ruim record loading
- refactor the usages of getIMSI(), getGid1(), getGid2(),
and getServiceProviderName()
- fix potential crash issue in SIMRecord

Test: Manual
Bug: 32591388
Change-Id: I6dde2c29ca2f5c1dc55807e244260891ace08838
Merged-In: I6dde2c29ca2f5c1dc55807e244260891ace08838
(cherry picked from commit 1f4fd861)