[runtime] CDC YAML supports inline Python UDF definition

[yuxiqian]

This PR provides the ability to write inline Python UDFs with YAML pipeline jobs. It could be used like this:

transform:
  - source-table: db.users
    projection: ID, py_normalize(EMAIL) AS EMAIL_NORM, py_accumulate(AGE) AS acc

pipeline:
  user-defined-function:
    - name: py_normalize
      classpath: org.apache.flink.cdc.python.PythonUdf
      options:
        python-executable: /usr/bin/python3
        source: |
          def eval(s: str) -> str:
            return s.strip().lower()
    - name: py_accumulate
      classpath: org.apache.flink.cdc.python.PythonUdf
      options:
        python-executable: /usr/bin/python3
        source: |
          total = 0
          def eval(x: int) -> int:
            global total
            total += x
            return total

The wrapper itself is implemented as a Java UDF as well. No changes are made in the existing framework except the following:

• Runtime UDF binding names are slightly changed to allow defining multiple UDFs with the same class.
• Added an overload function for UserDefinedFunction#getReturnType to pass extra context info.