Enhancement: Node Default Monitor Support

[evanatuo]

Is your feature request related to a problem? Please describe.

When deploying LTMs, I have to set a default node monitor in the UI after provisioning has completed.

Describe the solution you'd like

A default monitor class which allows you to set the default monitor type from available monitors on the LTM (e.g. gateway_icmp)

Describe alternatives you've considered

Currently as a workaround, I'm doing this in a pipeline with the command modify ltm default-node-monitor rule gateway_icmp