Add start component type to start info

Start component provides a concise and correct way to determine which component
type (activity/service/broadcast/content provider) this start was for. Component
type is one of the key ways that start info can be use for optimizing startup
path. This cannot be correctly inferred from reasons alone as some reasons, like
alarm, can occur for multiple component types.

Test: run startinfo unit tests, dump records and spot check
Bug: 350063699
Flag: android.app.app_start_info_component
Change-Id: I5c8da22161b46f48442c466fe153ef6349aeb2f1