TOOLS-4263 Convert mongorestore oplog-replay edge-case tests to Go

[autarch]

The JS -> Go mapping (all under test/qa-tests/jstests/restore):

• oplog_replay_conflict.js -> TestOplogReplayConflict
  (an embedded oplog plus --oplogFile must fail and apply no data)
• oplog_replay_priority_oplog.js -> TestOplogReplayPriorityOplog
  (only the higher-priority --oplogFile entries are applied)
• oplog_replay_noop.js -> TestOplogReplayNoop
  (noop entries are skipped, inserts applied)
• preserve_oplog_structure_order.js -> TestOplogReplayPreservesComplexIDOrder
  (an update op with a multi-field subdocument _id preserves field
  order; the doc is pre-inserted on 8.1+ per SERVER-88158)
• oplog_replay_size_safety.js -> TestOplogReplaySizeSafety
  (reduced matrix: 50k small ops + 8 ~1MB ops; the JS swept up to a
  million ops)

This also moves some fixtures under mongorestore/testdata. Move fixtures dump_oplog_conflict, dump_local_oplog, dump_with_noop_in_oplog, dump_with_complex_id_oplog, and extra_oplog.bson into mongorestore/testdata/.

The oplog_replay_local_rs.js and dumprestore7.js tests are not included in this conversion; they require a replica-set topology and will be converted separately.

[autarch]

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• TOOLS-4263 Convert mongorestore oplog-replay edge-case tests to Go #1048 👈 (View in Graphite)
• TOOLS-4263 Convert mongorestore invalid-input tests to Go #1046 : 1 other dependent PR (#1060 )
• TOOLS-4263 Delete JS tests fully covered by existing Go tests #1041
• TOOLS-4263 Add a Go test that we preserve indexes when restoring with a non-admin user on a per-data basis #1047
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