component-base: replace url in rest client metrics
component-base: replace url in rest client metrics

The `rest_client_request_duration_seconds` and
`rest_client_rate_limiter_duration_seconds` metrics have a url label
that used to contain the whole uri of the request. This is very
dangerous and can lead to cardinality explosions since its values aren't
bounded. We don't really need to expose the whole uri since these
metrics are used to mesure the availability of the different proxy in
front the apiserver. The most valuable information is the host to be
able to differentiate between the different proxy. In the future, we
might also want to add the path to be able to add some granularity, but
since there is no immediate use case for that, so there is no need to
add it now.

Signed-off-by: Damien Grisonnet <dgrisonn@redhat.com>

Kubernetes-commit: a188f5bf7e2b1fc6b7be9e1386f0506d3033e2a8

kubernetes/component-base