Add long as a target type for convert_entry_type processor

[Utkarsh-Aga]

Is your feature request related to a problem? Please describe.
Currently, date processor parses the timestamp and stores in destination field which is of String type.

Describe the solution you'd like
In scenario's, when the integer value of destination field is needed, we could use this convert_entry_type processor to convert the destination field to long, because using integer is not feasible for epoch times.

[Utkarsh-Aga]

If the team is okay to have this feature, then I would be more than happy take a shot at it and raise a PR.

[dlvenable]

@Utkarsh-Aga , I agree with you. Being able to convert to a long makes sense and is needed at certain times. We'd be happy to review and accept a PR. I'll assign this to you.

[Utkarsh-Aga]

Sure, Thank you.