Apply context lock pattern to LatestPersistedSealedResult

[mts1715]

Closes #7611
Aligns LatestPersistedSealedResult with the storage layer's context lock pattern introduced in #7364.

Changes
Updated LatestPersistedSealedResult.BatchSet() to accept lockctx.Proof as first parameter
Added runtime lock verification - requires caller to hold LockInsertCollection
Removed internal batchMu sync.Mutex in favor of external lock management via lockctx
Updated all tests to use storage.NewTestingLockManager() and unittest.WithLock()
Updated mocks to reflect new signature

Rationale
LockInsertCollection is used because:
BatchSet() is called within BlockPersister.Persist() which already holds this lock
All persistence operations (collections, events, results, progress) are committed in a single atomic batch
Collections storage requires LockInsertCollection for transaction indexing consistency
This ensures atomicity: either all data persists together or none