Global execution feature in the New Kibana Alerting Experience

**What the feature is (as Title)**
Global execution feature in the New Kibana Alerting Experience

**Value proposition**
When alerting misbehaves, the hardest part is often finding where in the pipeline things broke, not whether something is wrong. Rule runs, recoveries, no-data checks, action policy matching, throttling, workflow dispatch, and Task Manager health live on different surfaces with no clear link between them. The Global alerting executions page brings cross-rule visibility into one place. Users see execution KPIs (total runs, failures, failure rate, top failing rules and action policies), a filterable execution list across the full alerting flow, and Task Manager health signals with guidance on what to do next.

**Expected outcome**

On-call and platform engineers can confirm in under a minute whether alerting itself is healthy during an incident, instead of guessing which rule to open first. From incident triage to weekly hygiene reviews, teams can spot platform-wide problems quickly, drill into a specific rule without losing context, and follow execution end to end instead of reconstructing it from scattered pages.