Enhancements to list_to_map processor

[oeyh]

Description

Adds some enhancements to to list_to_map processor:

• adds use_source_key and extract_value option to dynamically extract values and put them in a list under the source key
• adds tags_on_failure option to add tags when events failed to process
• simplifies existing code that uses JsonNode unnecessarily (see this comment on original PR)

Issues Resolved

Resolves #3867

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
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[asifsmohammed]

Logic looks good, please use final keywords when ever possible.

[kkondaka]

Please document the new config options in README.md.

Also, provide one example in the README.md for each of the options