This series adds support for reporting consumed capacity in BatchGetItem operations in Alternator.
It includes changes to the RCU accounting logic, exposing internal functionality to support batch-specific behavior, and adds corresponding tests for both simple and complex use cases involving multiple tables and consistency modes.
Need backporting to 2025.1, as RCU and WCU are not fully supported
Fixes#23690Closesscylladb/scylladb#23691
* github.com:scylladb/scylladb:
test_returnconsumedcapacity.py: test RCU for batch get item
alternator/executor: Add RCU support for batch get items
alternator/consumed_capacity: make functionality public