[FEATURE] Support grok command in PPL

[joshuali925]

Is your feature request related to a problem?
PPL currently supports parse command that allows user to extract text from a field with regex pattern. But regex is difficult to write while many extracted patterns are likely to be existing patterns. Supporting grok can make this easier.

What solution would you like?
Allow extracting text using java-grok similar to current parse command.

What alternatives have you considered?
A clear and concise description of any alternative solutions or features you've considered.

Do you have any additional context?
Add any other context or screenshots about the feature request here.

[penghuo]

I think we could add grok as a method in parse command.

1. I feel adding a lots of command will confuse customer.
2. If customer require grok command in future, we could add it later, there is no one way door.