fix: Rescope Explore::DependenciesController to instance-wide rather than org-wide, drop org to sbom association

What does this MR do and why?

Rescopes Explore::DependenciesController to instance-wide rather than org-wide. Drops Organization#sbom_occurrences scope and simplifies overall permissions

Fixes Resolve sbom_occurrences cross join issues to o... (#477829 - closed)

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Database Review

Before

SELECT "sbom_occurrences".*
FROM "sbom_occurrences"
INNER JOIN "projects"
  ON "sbom_occurrences"."project_id" = "projects"."id"
WHERE "projects"."organization_id" = 1
  AND "projects"."archived" = FALSE

After

SELECT sbom_occurrences

https://console.postgres.ai/gitlab/gitlab-production-main/sessions/33499/commands/103186

SELECT "sbom_occurrences".*
FROM "sbom_occurrences"
WHERE "sbom_occurrences"."archived" = FALSE
ORDER BY "sbom_occurrences"."id"
ASC LIMIT 21