Move all test files of metricbeat modules to their own directories

[jsoriano]

Currently there are some test files that are in a common directory, and we also have big shared docker compose files used for tests. After some changes done lately we could move all this data to the module itself, so all test information resides in the same place as the module code. This will help to identify what files are associated to each module, and to better know what files will need to be added when creating a new module. This will also help on development and CI to identify what tests need to be run for each module.

This includes:

• Move python tests to the module directories. (Move all python test files #14624)
• Move docker-compose definitions to a new docker-compose.yml file in each module directory. (Move all python test files #14624)
• Add a _meta/supported-versions.yml file to the module.
• Use _meta/supported-versions.yml for the versions used in system tests. (Move all python test files #14624)
• Update dev documentation

Secondary goals

• Add templates for files to the module generator for integration and system tests, supported-versions.yml and docker-compose.yml.
• Use supported-versions.yml as input for docs.

For more context, look at these issues:

• Improvements in metricbeat modules integration tests #12909 and Support per-module docker compose files for metricbeat tests #13186 - Support for separated docker compose definition and example migration of Apache module.
• Read build args for metricbeat system tests from file #14520 - Use of supported-versions.yml file for running system tests on all the supported versions of a service, examples with mysql and apache.
• ci(jenkins): add CI life cycle for Metricbeat apache module's docker images #14355 and Add target to build images from supported-versions.yml file #14587 - Use of supported-versions.yml file to prebuild docker images in CI for integration, system and E2E tests.

[jsoriano]

Closing this as we have the focus on integrations now. If further changes are done in modules testing it will be done from the point of view of integrations.