Add @FlaggedApi to PackageTagsList.Builder

When @FlaggedApi is annotated on a parent class, all child interfaces, classes, and methods effectively inherit this annotation's effect. However, due to Metalava's issues generating the annotation in API signature files, the annotation is being added explicitly.

Flag: android.location.flags.change_get_adas_allowlist_from_hidden_to_system
Test: Build all the public and system API
Bug: 362287534
Change-Id: I695e6831f1b9765433046434c3a80038d864c722