Allow fields to be ignored from gyro diff

[deepanjan90]

Is your feature request related to a problem? Please describe.
A number of times there are fields (output) that change values based on resource updates which causes the state file to change.
A common example would be a date field like updated-on that changes on every update of the resource. Not always are we interested in that change and would be nice to avoid state changes based on that.

Describe the solution you'd like
An annotation baed approach where we can declaratively select fields to ignore so so that gyro does not pick up changes.