Add docs and example for OTel JVM runtime metrics

[zeitlinger]

Alternative for #1854

Summary

• Add documentation for using OpenTelemetry's runtime-telemetry module as an alternative to prometheus-metrics-instrumentation-jvm for JVM metrics following OTel semantic conventions
• Add a runnable example project (examples/example-otel-jvm-runtime-metrics) demonstrating combined Prometheus + OTel runtime metrics on a single /metrics endpoint
• Document RuntimeMetricsBuilder configuration options (captureGcCause(), emitExperimentalTelemetry())
• Cover standalone setup, combined setup with PrometheusMetricReader, Java 17 JFR support, and OTel-to-Prometheus metric name mapping

Test plan

• mise run build passes
• mise run lint:super-linter passes
• Manual: java -jar examples/example-otel-jvm-runtime-metrics/target/example-otel-jvm-runtime-metrics.jar then curl localhost:9400/metrics shows both uptime_seconds_total and jvm_* metrics

[zeitlinger]

not related to this PR, but a good opportunity to fix - last time I merged with this check failing and I didn't like it

[Copilot]

Pull request overview

Adds documentation and a runnable example showing how to expose OpenTelemetry JVM runtime metrics (runtime-telemetry) alongside Prometheus Java client metrics on a single /metrics endpoint, including configuration notes and name-mapping guidance.

Changes:

• Adds a new runnable Maven example module demonstrating combined Prometheus + OTel JVM runtime metrics on one endpoint.
• Adds a new docs page describing standalone vs combined setup, configuration toggles, Java 17 JFR notes, and OTel→Prometheus metric name mapping.
• Adjusts link-lint workflow behavior to handle links pointing at main for newly added files.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
examples/pom.xml	Adds the new example module to the examples reactor build.
examples/example-otel-jvm-runtime-metrics/src/main/java/io/prometheus/metrics/examples/otelruntimemetrics/Main.java	Demonstrates wiring PrometheusMetricReader into a shared PrometheusRegistry and serving via HTTPServer.
examples/example-otel-jvm-runtime-metrics/pom.xml	Adds OTel SDK/exporter/runtime-telemetry dependencies and shaded runnable jar packaging.
examples/example-otel-jvm-runtime-metrics/README.md	Provides build/run instructions and expected /metrics output excerpts.
docs/content/otel/jvm-runtime-metrics.md	New documentation page describing OTel runtime metrics usage patterns and options.
docs/content/instrumentation/jvm.md	Adds a note linking to the new OTel runtime metrics alternative docs.
.github/workflows/lint-rest.yml	Updates permissions and adds PR-branch URL remapping for link checking.

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[jaydeluca]

couple small nitpicks but lgtm