Support parsing of xml fields in Events

[graytaylor0]

Is your feature request related to a problem? Please describe.
As a user who sends XML in specific fields in Events to my Data Prepper pipelines, I would like to be able to parse the xml

Describe the solution you'd like
A new processor to parse xml.

Describe alternatives you've considered (Optional)
A clear and concise description of any alternative solutions or features you've considered.

[dlvenable]

@graytaylor0 , I'm not sure what it means to "decrypt" XML. XML is just a format.

I think we could resolve this by making a new parse_xml processor. It would be similar to the parse_json and parse_ion processors. And it should be able to use the same framework since Jackson has an XML parser.

- parse_xml:
     source: xmlstring
     pointer: /xml

The XML data can be encrypted in one of two ways. 1) The whole XML binary is encrypted; or 2) specific fields are encrypted as base64. Depending on how the data is encrypted, users could either: 1) Decrypt this before the parser. Or 2) decrypt specific fields after parsing it.

[cameronattard]

Related: #4024