Put metric interval feature in GA

[razum90]

Is your feature request related to a problem? Please describe.
So that I can safely use the feature in production.

Describe the solution you would like
Put metric interval feature in GA and update docs at https://learn.microsoft.com/en-us/azure/azure-monitor/app/java-standalone-config#metric-interval

Additional context
As per request from Didier G in the application insights team.

[heyams]

We'll GA this feature in our next release. Thanks.

[heyams]

@razum90 metric interval has been GA in 3.4.9