Feature flag to enable License Scanning SBOM scanner

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 !105747 (merged) 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: #384932 (closed)

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 Use License Scanning service (&8532 - closed).
• The backend should raise a Not implemented error (unless #384932 (closed) 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 Use License Scanning service (&8532 - closed).
• Make sure that there's no regression.