OperationSource
OperationSource = readonly
Operation[] |Iterable<Operation> |AsyncIterable<Operation>
Operations to submit, in order.
Aggregate commit.apply normalizes and preflights an array as a whole before
its first append; iterable input is validated one chunk at a time. The
full-duplex commit.applyStreaming path validates every source incrementally,
including arrays, because committed response groups may arrive while later
input is still being produced.