Currently, all batching, retry, server and connection selection, single-operation execution, and error handling logic are part of the giant 500-line Operation.Execute function. That function is becoming unmaintainable as more and more logic is added to it (e.g. RTT short-circuit, memory buffer reuse, additional error handling, etc). Difficulty maintaining Operation.Execute has also contributed to several bugs (GODRIVER-2677, GODRIVER-2768) and Go driver version retractions (v1.11.0 - v1.11.2).

Refactor Operation.Execute into functions and/or types with separate concerns. For example, it might make sense to create a function and/or type for each of:

1. Batching
2. Retry
3. Single-operation execution

Definition of done:

• Split Operation.Execute into functions and/or types that separate at least batching, retry, and single-operation execution concerns.
• Add tests that assert the behavior of each concern individually.