pkg/maps/metricsmap: Add a new userspace pkg/maps/metricsmap to access BPF metrics maps.
pkg/maps/metricsmap: Add a new userspace pkg/maps/metricsmap to access BPF metrics maps.

This commit adds a new pkg/maps/metricsmap which defines the userspace interface and
functions to access the BPF metrics maps.

Fixes: #4155
Related-to: #3284
Related-to: #3337
Signed-Off-By: Manali Bhutiyani <f91afadb65fa57d2313cebbfecb7de1f482fe10f@covalent.io>

scanf/cilium,eloycoto/cilium,cilium/cilium,eloycoto/cilium,eloycoto/cilium,tklauser/cilium,tgraf/cilium,eloycoto/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,cilium-team/cilium,cilium/cilium,scanf/cilium,michi-covalent/cilium,tklauser/cilium,cilium/cilium,michi-covalent/cilium,scanf/cilium,cilium-team/cilium,tgraf/cilium,scanf/cilium,tgraf/cilium,tklauser/cilium,michi-covalent/cilium,cilium/cilium,eloycoto/cilium,eloycoto/cilium,scanf/cilium,scanf/cilium,michi-covalent/cilium,eloycoto/cilium,cilium/cilium,tklauser/cilium,tgraf/cilium,scanf/cilium,michi-covalent/cilium