Migrate MySQL Enterprise Audit log

[P1llus]

This issue has been created to ensure that the merge of the OSS and the X-Pack mysql module happens.
OSS:
https://github.com/elastic/beats/tree/master/filebeat/module/mysql
X-Pack:
elastic/beats#22273

All Changes

• Change follows development guidelines
• Supported versions of the subject being monitored are documented
• Supported operating systems are documented (if applicable)
• System tests exist
• Documentation
• Fields follow ECS and naming conventions
• At least a manual test with ES / Kibana / Agent has been performed.
• The required Kibana version is set to the lowest version used in the manual test.

Log datasets

• Pipeline tests exist (if applicable)
• Test log files exist for the grok patterns
• Generated output for at least 1 log file exists

[elasticmachine]

Pinging @elastic/security-external-integrations (Team:Security-External Integrations)

[andresrc]

This should be coordinated with #365

[andrewkroh]

The myqsl package has been created so for this we need to migrate the Filebeat audit log data stream.

[botelastic]

Hi! We just realized that we haven't looked into this issue in a while. We're sorry! We're labeling this issue as Stale to make it hit our filters and make sure we get back to it as soon as possible. In the meantime, it'd be extremely helpful if you could take a look at it as well and confirm its relevance. A simple comment with a nice emoji will be enough :+1. Thank you for your contribution!