Add project CI/CD settings changes to audit events

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We should track configuration changes made to a project's CI/CD settings.

General pipeline settings
Auto DevOps settings
Runners settings (also in https://gitlab.com/gitlab-org/gitlab-ee/issues/8074 for projects and groups)
Secret variables (also in https://gitlab.com/gitlab-org/gitlab-ee/issues/8070 for projects and groups)
Pipeline triggers

Project CI/CD setting:

Update Git strategy for pipelines from clone/fetch to clone/fetch
Update the timeout threshold from x to z
Add custom CI config path to `my_path/.gitlab-ci.yml``
Enabled/Disabled public access to pipelines and job details, including output logs and artifacts
Enabled/Disabled auto-cancel redundant, pending pipelines
Enabled/Disabled test coverage parsing using expression example_\(\d+.\d+\%\)

Auto DevOps:

Protected Environments:

Protected/Unprotected environment x, add/remove user_or_role_name to be allowed to deploy

Runners:

Environment variables:

Clicking "Reveal values"
Add/Remove environment key key_name and set as protected/unprotected to environment_name

Not displaying the value:

Update environment variable status for key_name from protected/unprotected to protected/unprotected

Pipeline triggers:

Add/Remove/Update trigger description from description_text to description_text

License Management

Add/Remove/Update license from/to license_type to license_type and add to approve/blacklist

Here's an example of how it could look like in a table view:

Author	Action	Target	At
John Doe	Update git strategy for pipelines from clone to fetch, entity path user/project	project_name	2019-01-22 12:43:20 UTC