layers: Add component awareness to SC interface matching

layers: Add component awareness to SC interface matching

- Adds more tests for mismatch by component and by location
- Removes dead handling of builtins (we only care about collecting builtin /decorations/ to aid in the interface block handling;
    we don't really care about producing the set of builtins used overall.)

Some SC error messages change slightly, as interstage locations now include the component index.

Fixes internal bug 26609754

V2: Remove dead code

Signed-off-by: Chris Forbes <chrisforbes@google.com>