docs(json-specs): improve descriptions and examples

[Yqnn]

What does this PR do?

Fix minor issues in spec files:

• 9848cc8
  • Make the descriptions of the following fields compatible with markdown:
    • custom_queries
    • auth_type
    • metrics (openmetrics)
    • extra_metrics (openmetrics)
    • share_labels (openmetrics)
    • custom_queries (elastic)
  • Add an example on the following fields:
    • metrics (openmetrics)
    • share_labels (openmetrics)
    • custom_queries (elastic)
    • expected_mode (zk)
• 409d469 regenerate examples
• b8c45c2 add changelogs

---

Impact of the changes on the integration configuration UI:

Before	After

Motivation

https://datadoghq.atlassian.net/browse/FA-1028

Review checklist (to be filled by reviewers)

• Feature or bugfix MUST have appropriate tests (unit, integration, e2e)
• 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 90.23%. Comparing base (7ff5122) to head (b8c45c2).
⚠️ Report is 16 commits behind head on master.

Additional details and impacted files

Flag	Coverage Δ
cassandra	?
confluent_platform	?
elastic	93.92% <ø> (ø)
hive	?
hudi	?
ignite	?
jboss_wildfly	?
kafka	?
presto	?
solr	?
tomcat	?
weblogic	?
zk	82.30% <ø> (ø)

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[github-actions]

⚠️ Major version bump
The changelog type changed or removed was used in this Pull Request, so the next release will bump major version. Please make sure this is a breaking change, or use the fixed or added type instead.

[estherk15]

Non blocking, but just noticed that these don't line up.

Suggested change

	## ```
	## ```

[estherk15]

This is not a blocker, but noticed that the backticks aren't aligned for this field:

    ##     ```
    ##      extra_metrics:
    ##      - <METRIC_1>
    ##      - <METRIC_2>
    ##      ```