Add some metrics improvements (#15922)

* Define TCP and QUIC as `InternetProtocol` (no functional change).

* Group types. (No functional changes)

* Rename variables and use range syntax.

* Add `p2pMaxPeers` and `p2pPeerCountDirectionType` metrics

* `p2p_subscribed_topic_peer_total`: Reset to avoid dangling values.

* `validateConfig`:
- Use `Warning` with fields instead of `Warnf`.
- Avoid to both modify in place the input value and return it.

* Add `p2p_minimum_peers_per_subnet` metric.

* `beaconConfig` => `cfg`.

https://github.com/OffchainLabs/prysm/pull/15880#discussion_r2436826215

* Add changelog

---------

Co-authored-by: james-prysm <90280386+james-prysm@users.noreply.github.com>

beacon-chain/p2p/peers/status.go

@@ -81,29 +81,31 @@ const (
 type InternetProtocol string
 
 const (
-	TCP  = "tcp"
-	QUIC = "quic"
+	TCP  = InternetProtocol("tcp")
+	QUIC = InternetProtocol("quic")
 )
 
-// Status is the structure holding the peer status information.
-type Status struct {
-	ctx                   context.Context
-	scorers               *scorers.Service
-	store                 *peerdata.Store
-	ipTracker             map[string]uint64
-	rand                  *rand.Rand
-	ipColocationWhitelist []*net.IPNet
-}
+type (
+	// Status is the structure holding the peer status information.
+	Status struct {
+		ctx                   context.Context
+		scorers               *scorers.Service
+		store                 *peerdata.Store
+		ipTracker             map[string]uint64
+		rand                  *rand.Rand
+		ipColocationWhitelist []*net.IPNet
+	}
 
-// StatusConfig represents peer status service params.
-type StatusConfig struct {
-	// PeerLimit specifies maximum amount of concurrent peers that are expected to be connect to the node.
-	PeerLimit int
-	// ScorerParams holds peer scorer configuration params.
-	ScorerParams *scorers.Config
-	// IPColocationWhitelist contains CIDR ranges that are exempt from IP colocation limits.
-	IPColocationWhitelist []*net.IPNet
-}
+	// StatusConfig represents peer status service params.
+	StatusConfig struct {
+		// PeerLimit specifies maximum amount of concurrent peers that are expected to be connect to the node.
+		PeerLimit int
+		// ScorerParams holds peer scorer configuration params.
+		ScorerParams *scorers.Config
+		// IPColocationWhitelist contains CIDR ranges that are exempt from IP colocation limits.
+		IPColocationWhitelist []*net.IPNet
+	}
+)
 
 // NewStatus creates a new status entity.
 func NewStatus(ctx context.Context, config *StatusConfig) *Status {