Add start info test for custom process name

Add test covering the start of an activity with a custom process name
and ensuring that a start info record is created and can be accessed.

Refactor fields into shared helper for use in both test activities.

Bug: 443344191
Test: atest ActivityManagerAppStartInfoTest with flag enabled and disabled
Flag: EXEMPT - new test only
Change-Id: I86e9eda9b30b85f06dc0c06c5d36b35220a23019
6 files changed