Jmx unit semconv alignment - Tomcat

[robsunday]

Changes:

1. Metric names made semconv aligned
2. Attribute names made semconv aligned
3. Metrics descriptions format standardized
4. tomcat.yaml moved from agent to library folder to make it reusable in all library dependants
5. Tomcat JMX metrics Integration test implemented. It utilize assertions and target system integration test framework ported by @SylvainJuge from opentelemetry-java-contrib

[robsunday]

[for reviewer] Tomcat metrics definition is tested in a much better way in TomcatIntegrationTest.java

[SylvainJuge]

By "much better way" here it means being tested against a real tomcat instance rather than trying to parse the yaml file to see if there are any errors.

[robsunday]

Moreover, it can now be easily tested with multiple tomcat versions

[SylvainJuge]

@robsunday #13597 has been merged, so you can update with current state of main to make diff simpler.

[SylvainJuge]

I think that processingTime and maxTime mbean attributes are related, so we should probably make sure their name reflect that, for example:

• tomcat.request.max.time for maxTime + tomcat.request.total.time for processingTime
• having the total or max not at the end of the metric name helps to avoid the "do not use total" rule in semconv
• alternatively, we could argue that the "do not use total" rule in semconv refers only to the _total and not total suffix and then use tomcat.request.time.max and tomcat.request.time.total but this might be harder to make people agree on this.

[SylvainJuge]

Suggested change

	metric: active_session.count
	metric: session.active.count

In addition to renaming I would suggest to add tomcat.session.active.limit updowncounter as it provides the configured limit if there is any or -1 if none is set, so using the negative value filtering would be appropriate for it.

As a side note, there are also the expiredSessions and rejectedSessions mbeans attributes that would be tempting to use for a tomcat.session.count with a metric attribute to provide breakdown per state on the total number of sessions but we would be making assumptions on the implementation, so I would not recommend that, also it prevents us from having tomcat.session.active.count and tomcat.session.active.limit.

[SylvainJuge]

Suggested change

	tomcat.thread_pool.name: param(name)
	tomcat.thread.pool.name: param(name)

This would be consistent with db.client.connection.pool.name defined in DB semconv.

[SylvainJuge]

Here we could also capture maxThreads as tomcat.thread.limit (updowncounter), but this could be done in another PR as an improvement.