Add Configure Log Analytics data retention initiative (Monitoring)

[claestom]

Add initiative: Configure Log Analytics data retention (Monitoring)

Custom initiative grouping the three retention policies (workspace, table, and Application Insights).

• References the member policies by GUID, so it must be deployed at the same scope as those definitions
• ⚠️ Depends on the three policy PRs merging first:
  • policy/law-workspace-retention
  • policy/law-table-retention
  • policy/appinsights-table-retention
• Source: https://github.com/claestom/law-retention-guardrails