feat: GitLab VendorBehavior (#8300)
### Description
Adds a GitLab service `VendorBehavior`, so that logs are aggregated into
groups.
This was initially part of https://github.com/vercel/turbo/issues/6188.
However, due to the special treatment required for the timestamps
indicating the start and end of log groups, a decision was made to
remove it from the initial task's scope.
### Testing Instructions
1. build turborepo binary
2. push an example monorepo to GitLab
3. run some turbo tasks in GitLab CI
4. check if logs are grouped into sections
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Co-authored-by: Chris Olszewski <chris.olszewski@vercel.com>
Co-authored-by: Chris Olszewski <chrisdolszewski@gmail.com>
