Add unit tests for ImsVideoCallProviderWrapper.

Specifically adding tests to ensure that the issue described in the bug
is handled correctly.

Test: Manual/unit
Bug: 35304446
Merged-In: I40fb4b7df15c55114bda506442e5efa0aefbd809
Change-Id: I40fb4b7df15c55114bda506442e5efa0aefbd809