test: adding JSON files from sessions and causal consistency

[paulocoghi]

This PR delivers full compatibility for Sessions, Causal Consistency, and Snapshot Reads (MongoDB 5.0+):

1. Snapshot Reads (snapshot-sessions.md):

   • Added support for snapshot: true and snapshot_time in Mongo::Session::Options and ClientSession.
   • Automated extraction and persistence of atClusterTime from server command responses (cursor.atClusterTime or top-level atClusterTime).
   • Automatically injects readConcern: { level: "snapshot", atClusterTime: ... } into all commands within snapshot sessions.
   • Enforced client-side wire version check (maxWireVersion >= 13) raising clean errors on pre-5.0 MongoDB versions.
   • Prohibited starting transactions inside snapshot sessions (Error::Transaction).

2. Causal Consistency (causal-consistency.md):

   • Updated WithReadConcern.mix_read_concern to propagate readConcern.afterClusterTime on all write commands (insertOne, updateOne, deleteMany, bulkWrite, etc.) outside of transactions when an operation_time exists on the session.

3. Unified Test Format Runner Updates:

   • Implemented new dispatcher operations: getSnapshotTime, assertSessionDirty, assertSessionNotDirty, assertSameLsidOnLastTwoCommands, and assertDifferentLsidOnLastTwoCommands.
   • Updated client and session entity instantiation in Runner to record CommandStartedEvents and resolve snapshotTime entity references.

Results:

• Passed: 332 specification tests passing (324 before this PR)