[Umbrella] Metrics Aggregator Implementation

[kerthcet]

What would you like to be cleaned:

• ai gateway support, we have implemented metrics aggregator implementation, but lack the support of ai gateway

• once ai gateway supports retrieving the date, we should have e2e tests to cover it.

[kerthcet]

/kind feature
/remove-kind cleanup
/assign

[kerthcet]

Some progress: working on the ai gateway right now.