Fix tcp.current_established/tcp.connections metric types

[clarkb7]

What does this PR do?

Send tcp.current_established/tcp.connections as gauge instead of rate/count

adds tests for metric types

Motivation

https://datadoghq.atlassian.net/browse/WINA-1086
metrics added in #18294 but this case was missed

Additional Notes

no changelog b/c it's a fix for something not yet released (to be released in 7.58

this bug creates INFO logs of the form

No value returned for check metric 'system.net.tcp.connections' on host 'WIN-N52UFIFM9PJ' and tags '': Rate value is negative, discarding it (the underlying counter may have been reset)

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• Changelog entries must be created for modifications to shipped code
• Add the qa/skip-qa label if the PR doesn't need to be tested during QA.
• If you need to backport this PR to another branch, you can add the backport/<branch-name> label to the PR and it will automatically open a backport PR once this one is merged

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.96%. Comparing base (1b58301) to head (76fbb0d).
Report is 8 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
activemq	?
cassandra	?
hive	?
hivemq	?
ignite	?
jboss_wildfly	?
kafka	?
network	93.51% <100.00%> (+0.03%)	⬆️
presto	?
solr	?

Flags with carried forward coverage won't be shown. Click here to find out more.

[JakeYankovich]

looks good to me! thanks

[datadog-agent-integrations-bot]

The backport to 7.58.x failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-7.58.x 7.58.x
# Navigate to the new working tree
cd .worktrees/backport-7.58.x
# Create a new branch
git switch --create backport-18764-to-7.58.x
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 990cc9bec8bb1a4b5b89bcdeca3118b24776488f
# Push it to GitHub
git push --set-upstream origin backport-18764-to-7.58.x
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-7.58.x

Then, create a pull request where the base branch is 7.58.x and the compare/head branch is backport-18764-to-7.58.x.