Feature flag to enable License Scanning SBOM scanner
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## Why are we doing this work
We need a feature flag to roll out the License Scanning SBOM Scanner, and to enable it in specific projects before making it the default.
## Further details
`LicenseScanning.scanner_class` introduce in https://gitlab.com/gitlab-org/gitlab/-/merge_requests/105747 always returns the `ArtifactScanner`. This needs to be change to return the `SbomScanner` when the new feature flag is enabled.
## Relevant links
- `LicenseScanning.scanner_class`: https://gitlab.com/gitlab-org/gitlab/-/blob/master/ee/lib/gitlab/license_scanning.rb#L21
- Implementation of the SBOM Scanner: https://gitlab.com/gitlab-org/gitlab/-/issues/384932
## Non-functional requirements
## Implementation plan
- [ ] Declare a new FF to enable License Scanning SBOM Scanner.
- [ ] Change `LicenseScanning` to use `SbomScanner` instead of `ArtifactScanner` when the FF is enabled.
## Verification steps
Check FF
- Enable FF for a specific project
- Use any License Scanning feature that's been refactored as part of https://gitlab.com/groups/gitlab-org/-/epics/8532+.
- The backend should raise a `Not implemented` error (unless https://gitlab.com/gitlab-org/gitlab/-/issues/384932 has been implemented).
Non-regression test
- Go to a projet where License Scanning has been configured, and that has License Scanning artifacts.
- Use any License Scanning feature that's been refactored as part of https://gitlab.com/groups/gitlab-org/-/epics/8532+.
- Make sure that there's no regression.
issue