Resolve uid / pid early during connection

This CL further clusters identity resolution in a single place in each
of connect / connectDevice / initializeShimMetadata. This will mean that
checking the validity of the provided AttributionSource can occur in
the same place as legacy caller identity resolution, and one flag check
will be needed in each caller to connectHelper.

Flag: EXEMPT Strict mechanical refactor
Bug: 190657833
Test: atest CtsCameraTestCases, Camera1 + Camera2 apps
Change-Id: I2ba8e78e7419e956151ed54d6a2a88f7946774ce