Fix NPE in map to list processor

[oeyh]

Description

Get rid of the use of List.of and Map.of to allow for null values in input map for map_to_list processor

Issues Resolved

Resolves #5341

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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[san81]

We are changing the existing behavior so we should make sure to update the documentation to reflect this change.

[oeyh]

We are changing the existing behavior so we should make sure to update the documentation to reflect this change.

Thanks for the review. To me, It's more like fixing an expected behavior than changing the existing behavior: it should be OK to have null values in the input map, but it was having NPE due to implementation (List.of and Map.of).