indexer.storage: Add tests on signature type for all indexer storage implems
Depends on D4272
Test Plan
tox (failing on type divergence which i don't get for now)
Migrated from D4273 (view on Phabricator)
Depends on D4272
tox (failing on type divergence which i don't get for now)
Migrated from D4273 (view on Phabricator)