Add metrics support

[hslatman]

This PR adds support for sending metrics to the CrowdSec LAPI, and integrates with Caddy's metrics.

Example configuration, enabling pushing metrics to the LAPI every 15 minutes (minimum recommended by CrowdSec), and adding CrowdSec module metrics to the Caddy metrics served on the /metrics endpoint.

	crowdsec {
        ...
		metrics_interval 15m
		enable_caddy_metrics
        ...
	}

After enabling the metrics, adding two decisions manually, and hitting from those IPs, the reported values should look like this:

Bouncer Metrics (TestBouncer) since 2026-04-13 10:10:19 +0000 UTC:
╭────────────────────────────┬──────────────────┬─────────┬───────────╮
│ Origin                     │ active_decisions │ dropped │ processed │
│                            │        IPs       │ request │  request  │
├────────────────────────────┼──────────────────┼─────────┼───────────┤
│ CAPI (community blocklist) │            2.08k │       - │         - │
│ appsec                     │                0 │       - │         - │
│ console                    │                0 │       - │         - │
│ crowdsec (security engine) │                0 │       - │         - │
│ cscli (manual decisions)   │                2 │       6 │         - │
│ cscli-import               │                0 │       - │         - │
│ remediation_sync           │                0 │       - │         - │
├────────────────────────────┼──────────────────┼─────────┼───────────┤
│                      Total │            2.08k │       6 │        45 │
╰────────────────────────────┴──────────────────┴─────────┴───────────╯

And part of the /metrics endpoint:

$ curl http://127.0.0.1:2019/metrics | grep -i crowdsec_

# HELP crowdsec_appsec_lapi_requests_total The total number of calls to the CrowdSec LAPI AppSec component
# TYPE crowdsec_appsec_lapi_requests_total counter
crowdsec_appsec_lapi_requests_total 24
# HELP crowdsec_bouncer_lapi_requests_total The total number of calls to CrowdSec LAPI
# TYPE crowdsec_bouncer_lapi_requests_total counter
crowdsec_bouncer_lapi_requests_total{mode="stream"} 71
# HELP crowdsec_decisions_active The current number of active decisions
# TYPE crowdsec_decisions_active gauge
crowdsec_decisions_active{ip_type="ipv4",origin="CAPI"} 1947
crowdsec_decisions_active{ip_type="ipv4",origin="appsec"} 0
crowdsec_decisions_active{ip_type="ipv4",origin="console"} 0
crowdsec_decisions_active{ip_type="ipv4",origin="crowdsec"} 0
crowdsec_decisions_active{ip_type="ipv4",origin="cscli"} 0
crowdsec_decisions_active{ip_type="ipv4",origin="cscli-import"} 0
crowdsec_decisions_active{ip_type="ipv4",origin="remediation_sync"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="CAPI"} 129
crowdsec_decisions_active{ip_type="ipv6",origin="appsec"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="console"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="crowdsec"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="cscli"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="cscli-import"} 0
crowdsec_decisions_active{ip_type="ipv6",origin="remediation_sync"} 0
# HELP crowdsec_requests_blocked The total number of requests blocked
# TYPE crowdsec_requests_blocked counter
crowdsec_requests_blocked{ip_type="ipv6",origin="cscli",remediation="ban",server="layer4-[::1]:4444"} 4
crowdsec_requests_blocked{ip_type="ipv6",origin="cscli",remediation="ban",server="srv3"} 2
# HELP crowdsec_requests_processed The total number of requests handled
# TYPE crowdsec_requests_processed counter
crowdsec_requests_processed{ip_type="ipv6",server="layer4-[::1]:4444"} 5
crowdsec_requests_processed{ip_type="ipv6",server="srv2"} 14
crowdsec_requests_processed{ip_type="ipv6",server="srv3"} 26
# HELP crowdsec_requests_processed_per_module The total number of requests handled per module
# TYPE crowdsec_requests_processed_per_module counter
crowdsec_requests_processed_per_module{ip_type="ipv6",module="appsec",server="srv3"} 24
crowdsec_requests_processed_per_module{ip_type="ipv6",module="http",server="srv2"} 14
crowdsec_requests_processed_per_module{ip_type="ipv6",module="http",server="srv3"} 26
crowdsec_requests_processed_per_module{ip_type="ipv6",module="layer4",server="layer4-[::1]:4444"} 5