[Defend Workflows] Fix global packs not preserving policy references when creating new integrations or deleting policies

[szwarckonrad]

Fixes two bugs in osquery global pack management:

1. When creating a new osquery integration on a policy, global packs were losing references to existing policies because pack.references wasn't included in the SavedObject mapping
2. When deleting a policy, the delete callback had backwards filter logic that kept deleted policy references instead of removing them

Changes include comprehensive unit tests for both bug fixes.

Closes https://github.com/elastic/security-team/issues/14422

---

Co-authored with Claude Code

[elasticmachine]

Pinging @elastic/security-defend-workflows (Team:Defend Workflows)

[szwarckonrad]

Closing in favor of combined PR #241655 which includes this fix along with other osquery pack management improvements.

[elasticmachine]

💛 Build succeeded, but was flaky

• Buildkite Build
• Commit: af2a7bf

Failed CI Steps

• FTR Configs #72
• FTR Configs #101

Test Failures

• [job] [logs] FTR Configs #101 / Agents fleet_list_agent should return metrics if available and called with withMetrics
• [job] [logs] FTR Configs #72 / cases security and spaces enabled: basic Common migrations migrations 7.13 connector id extraction "before all" hook for "7.13 migrates user actions correctly for case with ID aa8ac630-005e-11ec-91f1-6daf2ab59fb5"

Metrics [docs]

✅ unchanged

cc @szwarckonrad