Capture output streams, along with their checksum in persisted file. This list needs to be sorted by generating plugin, so we understand who generated what.

Checksum (CRC32C is okay) should be calculated doing file writeout, so that we ride that IO operation.

State comparison needs to be updated to:

1. prune previous files when a generator binding goes away
2. prune files a generator did not generate this time

This should result in proper management of files good enough to enable incremental builds.