snapshots: refactor SnapshotRepository

[battlmonstr]

Refactor data access layer (DAL) logic and schema definition out of SnapshotRepository.

• schema is defined in snapshot_bundle.hpp and snapshot_type.hpp, indexes are defined in SnapshotBundleFactory
• find_segment is exposed with a snapshot type parameter
• view_xx_segments is replaced by iteration on bundles in a forward or reverse order (view_bundles_reverse)
• find_block_number is replaced by a new query object - TransactionBlockNumByTxnHashRepoQuery
  that runs TransactionBlockNumByTxnHashQuery on a view of bundles and returns the first match
• replace for_each_xx with nested for loops
• refactor queries to take SnapshotAndIndex

DataModel::read_transactions_from_snapshot: remove an extra reserve

[canepat]

I suggest moving this factory function into snapshot_bundle_factory_impl.hpp, so that we can use it everywhere and have a one-liner creation for SnapshotRepository as below:

SnapshotRepository snapshot_repo{settings, bundle_factory()};