Add snapshot_runtime_info module (#18199)

The `snapshot_runtime_info` module adds the `SnapshotRuntimeInfo` and
`SyncSnapshotRuntimeInfo` types to handle sharing runtime snapshot information
between threads; in particular: AccountsDb, Bank, SnapshotPackagerService, and
snapshot_utils.

runtime/src/lib.rs

@@ -34,6 +34,7 @@ pub mod rent_collector;
 pub mod secondary_index;
 pub mod serde_snapshot;
 pub mod snapshot_package;
+pub mod snapshot_runtime_info;
 pub mod snapshot_utils;
 pub mod sorted_storages;
 pub mod stake_weighted_timestamp;