What problem does this PR solve?

Issue Number: close #8891

Problem Summary:
When there are group by key in select item(a.k.a. first_row), tiflash have extra agg func, which cause unnecessary copy from HashMap to Column.

What is changed and how it works?

Basic idea:

Optimization-1 (with collation):
How:

1. Detect if there is a first_row agg func in the select item.
2. If so, ignore any agg func. If not, add the 'any' agg func.
3. Also, set key_from_agg_func to indicate that this key is equivalent to first_row/any agg func, which can avoid copying this key from the HashMap in subsequent operations. (check DAGExpressionAnalyzer::buildAggGroupBy)
4. If all keys are included in first_row/any (which is rare, but still can happens), will skip copy keys(template argument skip_serialize_key is true)

Optimization-2(no collation)
The above optimization happens when c2 has collation, if c2 has no collation(its type is not string), the process is as follows. So first_row is deleted.

Results:

1. 25% improvement
2. workload:
   1. 20M rows. More rows a different, it means we have very high NDV.
   2. 3 varchar columns, 3 decimal columns, 3 int columns (that means Aggregator will use HashMethodSerialized)

before:

after:

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

None