[jmx-scraper] add support for Solr

[SylvainJuge]

Description:

Adds Solr to jmx-scraper

• fix units for solr jmx metrics (in jmx scraper and jmx gatherer)
• add solr tests + yaml metrics

Part of #1362

[SylvainJuge]

This is currently failing due to a flaky wildfly test which is not related

WildflyIntegrationTest > endToEndTest(Path) FAILED org.opentest4j.AssertionFailedError: [no data point matched attribute set '[{server=default-server}, {listener=default}, {state=in}]' for metric 'wildfly.network.io'] expected: true but was: false at app//io.opentelemetry.contrib.jmxscraper.assertions.MetricAssert.lambda$hasDataPointsWithAttributes$2(MetricAssert.java:262) at app//io.opentelemetry.contrib.jmxscraper.assertions.MetricAssert.checkDataPoints(MetricAssert.java:188) at app//io.opentelemetry.contrib.jmxscraper.assertions.MetricAssert.hasDataPointsWithAttributes(MetricAssert.java:231) at app//io.opentelemetry.contrib.jmxscraper.target_systems.WildflyIntegrationTest.lambda$createMetricsVerifier$8(WildflyIntegrationTest.java:164) 

We will probably fix that in a separate PR, as it might require to relax a bit the metric assertions or wait for longer until the metric is properly reported.

[breedx-splk]

Looks good. Had just one small comment about unit and time vs. duration. Thanks!