Create a decoder processor to decode Event keys

Is your feature request related to a problem? Please describe.
As a user of Data Prepper, my Events contain keys that are encoded in different formats, such as gzip, base64, and protobuf (https://protobuf.dev/programming-guides/encoding/).

Sample Event

{
  "my_protobuf_key": "",
  "my_gzip_key": "H4sIAAAAAAAAA/NIzcnJVyjPL8pJAQBSntaLCwAAAA==",
  "my_base64_key": "SGVsbG8gd29ybGQ="
}

Describe the solution you'd like
A new processor called a decoder processor that can decode various encodings. The following configuration example would decode the three values in the example Event above

processor:
  - decoder: 
       key: "my_base64_key"
       # Can be one of gzip, base64, or protobuf
       base64:
  - decoder:
       key: "my_gzip_key"
       gzip:
  - decoder:
       key: "my_protobuf_key"
       protobuf:
          message_definition_file: "/path/to/proto_definition.proto"

Tasks

• #4016
• OTel decode processor
• Decode encoded data (base64)