cloudflare/ClickHouse

Commit

Add new query processing stage WithMergeableStateAfterAggregation

Process query until the stage where the aggregate functions were
calculated and finalized.

It will be used for optimize_distributed_group_by_sharding_key.

v2: fix aliases
v3: Fix protocol ABI breakage due to WithMergeableStateAfterAggregation
    Conditions >= for QueryProcessingStage::Enum has been verified, and they
    are ok (in InterpreterSelectQuery).