Add config spec templates for JMX integrations

[AlexandreYang]

Add jmx default config spec template used for jmx integrations.

Example usage for Hive: #5979

[codecov]

Codecov Report

Merging #5978 into master will decrease coverage by 8.26%.
The diff coverage is n/a.

Impacted Files	Coverage Δ
datadog_checks_dev/tests/test_docker.py	48.14% <0.00%> (-51.86%)	⬇️
datadog_checks_dev/tests/tooling/test_utils.py	68.75% <0.00%> (-31.25%)	⬇️
datadog_checks_dev/datadog_checks/dev/env.py	22.72% <0.00%> (-20.46%)	⬇️
datadog_checks_dev/datadog_checks/dev/docker.py	24.57% <0.00%> (-19.50%)	⬇️
datadog_checks_dev/tests/test_conditions.py	82.25% <0.00%> (-17.75%)	⬇️
...atadog_checks_dev/datadog_checks/dev/structures.py	68.85% <0.00%> (-13.12%)	⬇️
datadog_checks_dev/datadog_checks/dev/_env.py	54.79% <0.00%> (-9.59%)	⬇️
...atadog_checks_dev/datadog_checks/dev/subprocess.py	72.97% <0.00%> (-5.41%)	⬇️
...atadog_checks_dev/datadog_checks/dev/conditions.py	80.95% <0.00%> (-4.77%)	⬇️
...er/datadog_checks/openstack_controller/settings.py
... and 718 more

[ofek]

💜

[ofek]

Is this standard? If not, let's not put example

[AlexandreYang]

8686 seems used quite often for jmx, not sure it's standard, but it's quite common/typical:

• https://docs.oracle.com/cd/E19528-01/819-4892/ganjx/index.html
• https://www.ibm.com/support/knowledgecenter/en/SSHS8R_8.0.0/com.ibm.worklight.installconfig.doc/install_config/t_optional_config_app_server_tomcat.html
• https://thwack.solarwinds.com/t5/SAM-Documents/Understanding-Java-Remote-JMX-Initial-Setup-Config-Overview/ta-p/529969