Redesign checksum

[kindermax]

Consolidate checksum config under one directive

Before

command:
  x:
    checksum:
      - file.txt
    persist_checsum: true

  y:
    persist_checsum: true
    checksum:
      configs:
        - config.txt
      sql:
        - migration.sql 
  z:
    persist_checsum: true
    checksum_cmd: echo "1234"

After

1. All configuration under checksum
2. Use either files or sh
3. files can be a list of a map of file groups
4. Use persist: true instead of command-level persist_checksum

command:
  x:
    checksum:
      files:
        - file.txt
      persist: true
      sh: echo "1234"

  y:
    checksum:
      persist: true
      files:
        configs:
          - config.txt
        sql:
          - migration.sql 

  z:
    checksum:
      persist: true
      sh: echo "1234"