Support retry delays in Consul Connect routers

#### Feature Description

I'm not sure what the Envoy config would look like, but it would be really helpful if the retry delay and backoff strategy was configurable in a service router.

For example, being able to set an initial delay of 100ms with exponential retries would be nice.

#### Use Case(s)

```hcl
Kind = "service-router"
Name = "httpbin"
Routes = [
{
Destination {
ServiceSubset = ""
RequestTimeout = "1s"
NumRetries = 2
RetryOnConnectFailure = true
RetryOnStatusCodes = [500]
# NOTE: Fields to add
RetryDelay = "100ms"
RetryStrategy = "exponential"
}
},
]

```

Thanks folks!

The issue concerns Consul service-router destination settings and their Envoy configuration, with an HCL example proposing retry delay and strategy fields. Start by tracing how service-router configuration is translated into Envoy settings; done would require an agreed configuration design and verified retry behavior.

Written by the indexing model from the issue text.