Separate hidden API flags needed in sdk snapshots for S and T

Previously, the behavior of the stub_flags and all_flags properties
was different between S and T. In S they contained paths for the
complete set of stub flags and all the encoded flags. However, in T
they contained filtered sets of flags which if used in S would prevent
build checks from detecting possible inconsistencies. Also, a new
signature_patterns property was added in T that is not supported in S.

This change creates separate properties/files for T and reverts the
behavior of the properties/files that were added in S back to how they
behaved in S. The new properties are called filtered_stub_flags and
filtered_flags.

The S and T properties are tagged with the appropriate
supported_build_releases tag to ensure that they are only output when
specifically targeted.

Bug: 197842263
Test: m nothing
Change-Id: Iec8b9c539796c507245b69c0aed980fde6d8694f