Builder pattern for MediaProjectionConfig

Introduce a builder pattern for
MediaProjectionConfig, allowing more flexibility for the type of
configuration need by the requesting application, in preparation for the
content sharing option in a follow-up CL.

Also adding some documentation fix and moving readding the CTS in
presubmit.

Test: atest CtsMediaProjectionTestCases:MediaProjectionConfigTest
Flag: com.android.media.projection.flags.app_content_sharing
Bug: 398757866
Change-Id: I0e048c47605fe06bf49e032f387d4009750e5f02