There were two cache replay code exists, one for cache replay from
swift-frontend, the other for replay using C API from libSwiftScan. It
is easy to forget to update one copy when new specialized cache replay
logic is added for some output kinds. Now unify the replay logics to a
single location to avoid confusion. This is a rewrite of the existing
logic and NFCI.
Instead, each scan's 'ModuleDependenciesCache' will hold all of the data corresponding to discovered module dependencies.
The initial design presumed the possibility of sharing a global scanning cache amongs different scanner invocations, possibly even different concurrent scanner invocations.
This change also deprecates two libSwiftScan entry-points: 'swiftscan_scanner_cache_load' and 'swiftscan_scanner_cache_serialize'. They never ended up getting used, and since this code has been largely stale, we are confident they have not otherwise had users, and they do not fit with this design.
A follow-up change will re-introduce moduele dependency cache serialization on a per-query basis and bring the binary format up-to-date.
