Currently, the Cilium Operator only uses the metrics registry
of the `controller-runtime` as base registry if Gateway API
functionality is enabled. This has historic reasons as Gateway
API functionality was the first module that used `controller-runtime`
for its controllers.

In the meantime, other modules (Ingress Controller, Secret Sync, ...)
are using the `controller-runtime` too - but the metrics registry of
the library is still only used if Gateway API is enabled. In these
cases, the metrics of the `controller-runtime` library
(https://book.kubebuilder.io/reference/metrics-reference) aren't exposed.

Therefore, this commit changes the behaviour, that the metrics registry
of the `controller-runtime` library is always used as the base registry.

Note: Unfortunately, the `controller-runtime` library configures the base
registry to have Go runtime metrics included by default
(https://github.com/cilium/cilium/blob/main/vendor/sigs.k8s.io/controller-runtime/pkg/internal/controller/metrics/metrics.go#L91-L92).
Therefore, this Go metrics collector has to be removed from the metrics
registry before registering a new Go metrics collector with custom Go
runtime metrics enabled. Otherwise the registration fails because
some Go runtime metrics are registered twice.

Related PRs:
- cilium#28931 (extract `controller-runtime` integration into its own Hive Cell)
- cilium#29245 (export go runtime sched latency metrics)

Signed-off-by: Marco Hofstetter <marco.hofstetter@isovalent.com>