Exponential backoff for reconciler requests

[SinghVikram97]

What type of PR is this?
Cleanup and Fix

Which issue does this PR fix:
Fix HandleReconcileError function to enable exponential backoff.
Incase of transient errors from lattice apis keep static 10 seconds delay.

Exponential backoff is problematic here because for operations like target group deletion where target draining takes time, this results in unnecessarily long delays in reconciliation.

What does this PR do / Why do we need it:
According to the docs

 If the returned error is non-nil: the Result is ignored and the request will requeued using exponential backoff unless error is a terminal error If the error is nil: the returned Result has a non-zero result RequeueAfter, the request will be requeued after the specified duration. 

• Cleanup deprecated Requeue
• Remove returning Result if the returned error is non-nil
• In reconcile.go we check if err is of type RetryError but since RetryError is just an alias for err type, all error types satisfy that if condition which leads to 20 second requeue delay for all errors. Refactored NewRetryError function to return RequeueNeededAfter error type instead.
• Remove RetryErr which created err with Lattice_Retry error message with NewRetryError function call which returns a custom error type to fix type comparisons.

If an issue # is not available please add repro steps and logs from aws-gateway-controller showing the issue:
#462

Testing done on this change:

make presubmit and make e2e-test run successfully.

Automation added to e2e:

N/A

Will this PR introduce any new dependencies?:

No

Will this break upgrades or downgrades. Has updating a running cluster been tested?:
No

Does this PR introduce any user-facing change?:

No

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[rlymbur]

Can you add unit tests and an integration test to validate that the backoff is working as expected?

[rlymbur]

Are these the non-retriable?

[SinghVikram97]

These are retriable. For example when target group status is create in progress. But the default exponential backoff starts with 5ms which might be too aggressive for lattice apis. So that's why kept it as 10 seconds.