Add changelog and versioning to integration test project
Proposal
Now that Replace c and go downstreams with integration-t... (gitlab-org/security-products/analyzers/semgrep!157 - merged) has been completed, we have multiple teams (groupstatic analysis and groupcomposition analysis) that rely on the integration-test project.
At the moment, when an MR is merged in the integration test project, the updated image is immediately pushed to registry.gitlab.com/gitlab-org/security-products/analyzers/integration-test:stable. This means that there's no way to pin to a specific version of the integration test project, so if we want to make a breaking change, we need to ensure all teams using the integration test project update their codebase at the same time. In order to remove this limitation, and allow teams to update at their own pace, we need to support versioning in the integration test project.
The purpose of this issue is to add a CHANGELOG.md file and versioning to the integration test project, in order to improve documentation and reduce potential areas of friction between teams.