[ENT] Implement deletion for certifyVuln, hasSBOM and hasSLSA

[pxp928]

Description of the PR

• GraphQL updated to add Delete functionality (limited to certifyVuln, hasSBOM and hasSLSA)
• Expose Delete via the graphQL client
• Implement Delete for ENT backend
• Add unit tests for the new delete functionality

PR Checklist

• All commits have a Developer Certificate of Origin (DCO) -- they are generated using -s flag to git commit.
• All new changes are covered by tests
• If GraphQL schema is changed, make generate has been run
• If GraphQL schema is changed, GraphQL client updates/additions have been made
• If OpenAPI spec is changed, make generate has been run
• If collectsub protobuf has been changed, make proto has been run
• All CI checks are passing (tests and formatting)
• All dependent PRs have already been merged

[pxp928]

FYI @semmet95 and @kanchan-dhamane we can do the same for arrango now too. Created an issue for the KeyValue backend update here: #1983

[mrizzi]

While testing, the delete failed due to runtime error: invalid memory address or nil pointer dereference at guac/pkg/assembler/backends/ent/backend/sbom.go:542 for which I provided a partial fix (closing } and formatting missing)

[mrizzi]

@pxp928 thanks a lot: that's a great feature!