Store annotation during collation

- Only collate atoms in the specified module.

- Replace signature_to_modules with signatureInfoMap. This maps each
signature to another map keyed by field number and whose values are vector of
annotations.

Bug: 151102006
Test: stats-log-api-gen-test
Change-Id: I25bbe4883c8f7f86a06d04d27cd425367b6d65a0