Why op batching?

I want to read a key, then update conditional on the value in a single transaction.

Is there a performance or concurrency reason why the txn ops are batched together in `ngx_lua_resty_mdbx_ffi_execute`? Otherwise, I will modify each op to use a separate ffi call, so I can read before commit.

Start at the `ngx_lua_resty_mdbx_ffi_execute` entry point and read how transaction operations are batched. Trace whether a read followed by a conditional update can remain in one transaction, then review the issue's proposed separate FFI calls. Done means the batching rationale and an agreed approach for read-before-commit behavior are documented.

Written by the indexing model from the issue text.