4.x fix pinned meter type

[tjquinno]

Description

The recent addition of meters for virtual threads contains code that, when a pinned thread is reported, looks up the previously-registered Timer for recent pinned threads so it can update that timer. That look-up logic is flawed because it used the wrong name.

There is a Gauge for total pinned threads as well as a Timer for recent pinned threads(recent because as with all distribution summaries the timer's decays over time so "old" pinned thread events might eventually not influence the data).

The code that attempted to look up the timer used the gauge's name. Helidon metrics rejected the attempt to look up the gauge as a timer.

This PR corrects the name used for the look-up and also adds the correct scope tag and value to the look-up.

There is also a new test to make sure the look-up works correctly.

Here is the stack trace before the fix:

java.lang.IllegalArgumentException: Matching meter is of type io.micrometer.core.instrument.composite.CompositeGauge but io.helidon.metrics.api.Timer was requested
        at io.helidon.metrics.providers.micrometer.MMeterRegistry.meter(MMeterRegistry.java:333)
        at io.helidon.metrics.api.MeterRegistry.timer(MeterRegistry.java:135)
        at io.helidon.metrics.systemmeters.VThreadSystemMetersProvider.findPinned(VThreadSystemMetersProvider.java:119)
        at io.helidon.common.LazyValueImpl.get(LazyValueImpl.java:118)
        at io.helidon.metrics.systemmeters.VThreadSystemMetersProvider.recordThreadPin(VThreadSystemMetersProvider.java:146)
        at jdk.jfr/jdk.jfr.internal.consumer.Dispatcher$EventDispatcher.offer(Dispatcher.java:53)
        at jdk.jfr/jdk.jfr.internal.consumer.Dispatcher.dispatch(Dispatcher.java:185)
        at jdk.jfr/jdk.jfr.internal.consumer.EventDirectoryStream.processOrdered(EventDirectoryStream.java:253)
        at jdk.jfr/jdk.jfr.internal.consumer.EventDirectoryStream.processRecursionSafe(EventDirectoryStream.java:164)
        at jdk.jfr/jdk.jfr.internal.consumer.EventDirectoryStream.process(EventDirectoryStream.java:124)
        at jdk.jfr/jdk.jfr.internal.consumer.AbstractEventStream.execute(AbstractEventStream.java:261)
        at jdk.jfr/jdk.jfr.internal.consumer.AbstractEventStream$1.run(AbstractEventStream.java:284)
        at jdk.jfr/jdk.jfr.internal.consumer.AbstractEventStream$1.run(AbstractEventStream.java:281)
        at java.base/java.security.AccessController.doPrivileged(AccessController.java:400)
        at jdk.jfr/jdk.jfr.internal.consumer.AbstractEventStream.run(AbstractEventStream.java:281)
        at jdk.jfr/jdk.jfr.internal.consumer.AbstractEventStream.lambda$startAsync$1(AbstractEventStream.java:224)
        at java.base/java.lang.Thread.run(Thread.java:1583)

Documentation

Bug fix. No doc impact.