fix(security): inherit component_type on confinement gauge from ambient span

[vladimir-dd]

Summary

ConfinementConfig::set_confinement_gauge explicitly hardcoded component_type/component_kind labels from the calling sink's own Self::NAME. This is the only per-component metric in Vector that does this — every other one (e.g. component_sent_events_total, http_client_requests_sent_total) inherits component_type from the ambient tracing span the topology builder opens around the whole SinkConfig::build call (component_type = %sink.inner.get_component_name() in src/topology/builder.rs).

That's harmless when a sink is built directly, since Self::NAME matches the ambient span's type anyway. But it breaks when:

• One sink delegates its build to another SinkConfig::build internally (e.g. humio_metrics → humio_logs), or
• An external/downstream sink constructs a Vector sink config and calls .build() on it directly to wrap it.

In both cases the gauge reports the delegate's own component type instead of the wrapping sink's — while every other metric on that same build correctly reports the wrapping sink's type, because they don't override the ambient span.

Fix

Drop the explicit component_kind/component_type parameters from set_confinement_gauge entirely and let it inherit from the ambient span like every other metric. Updated all 27 call sites across the sink modules accordingly. No behavior change for sinks built directly; delegating/wrapping sinks now report the correct component type with no extra plumbing.

Vector configuration

N/A — this only changes internal metric tagging, not sink behavior or configuration surface.

Change Type

• Bug fix
• New feature
• Dependencies
• Non-functional (chore, refactoring, docs)
• Performance

Is this a breaking change?

• Yes
• No

Does this PR include user facing changes?

• Yes. Changelog fragment added at changelog.d/confinement_gauge_component_type_override.fix.md.
• No.

References

[vladimir-dd]

Closing as superseded by #25910, which merged into master after this branch was cut.

#25910 does a more complete rewrite of the same subsystem: it removes ConfinementConfig::set_confinement_gauge entirely and moves gauge ownership to the topology (RunningTopology::refresh_confinement_gauges), which tags the gauge from the topology's own knowledge of each top-level sink's declared component_type via a new SinkConfig::confinement_config() opt-in method — rather than from the ambient tracing span as this PR does. That structurally eliminates the class of bug this PR fixes (a delegate sink's build() can no longer report its own type in place of the wrapping sink's, since the gauge is never emitted from inside build() at all anymore), and it additionally fixes gauge expiry, which this PR didn't address.

No further action needed here — #25910 already covers this with its own test suite in src/topology/test/confinement_gauge.rs.