Add request handlers to v2 implementation

[randomvariable]

What would you like to be added:
Follow up from #131, add AWS request handlers to do the following:

• Add metrics
• Add rate limiting

@M00nF1sh , do you think it's worth re-implementing what's done in in https://github.com/aws/aws-app-mesh-controller-for-k8s/tree/master/pkg/aws for the above?

FWIW, I used the same metric formats in https://github.com/kubernetes-sigs/cluster-api-provider-aws/blob/master/pkg/cloud/metrics/metrics.go, so would be worth standardising.

Why is this needed:

/kind feature

[M00nF1sh]

@randomvariable Thanks for reaching out. I think we can keep same format(i'm open to new metrics if applicable) :D

[randomvariable]

@M00nF1sh Are we ok to copy the throttle package over to this repo and cluster-api?

[M00nF1sh]

@randomvariable of course. but i do think the throttle package needs some enhancements.
e.g. it should use endpointID instead of serviceName when throttling. since some service's serviceName have space within it.

[randomvariable]

/assign

[nckturner]

I spoke with @jaypipes and he is going to create a repository under the aws organization to put the throttle package and any other widely shared utils. @M00nF1sh WDYT about that?

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[randomvariable]

@jaypipes has any progress been made on creating the repo to include importable limiters?

[randomvariable]

/lifecycle frozen