How to add new functions

• Scalar function

• Aggregate function

Don't forget to add tests

• run: env REGENERATE_GOLDENFILES=1 cargo test after adding new functions

• build and run databend, prepare for logical tests:

  shellCopy

  make build
  make run-debug
  

• Add logic tests file in "tests/sqllogictests/suites/query/functions/*.test" and run:

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  cargo run \
  -p databend-sqllogictests \
  --bin databend-sqllogictests \
  -- \
  --handlers "http" \
  --run_dir functions \
  --run_file <test_file_name> \
  --debug \
  --parallel 2