Added health metrics for application load and database load (#2257)

* Added health metrics for application load

* Added health metrics for application load

* Fix unit tests

* Added more metrics

* Added few comments

* Added DatabaseLoad Scenario and address comments

* Fix unit tests

* fix unit tests

* Fix unit tests

* fix unit tests

* fix the mock

* Fix unit tests

src/Metrics/ScenarioConfig.ts

@@ -0,0 +1,47 @@
+import MetricScenario from "./MetricEvents";
+
+// Common phases shared across all scenarios
+export enum CommonMetricPhase {
+  Interactive = "Interactive",
+}
+
+// Application-specific phases
+export enum ApplicationMetricPhase {
+  ExplorerInitialized = "ExplorerInitialized",
+  DatabasesFetched = "DatabasesFetched",
+  DatabaseTreeRendered = "DatabaseTreeRendered",
+}
+
+// Combined type for all metric phases
+export type MetricPhase = CommonMetricPhase | ApplicationMetricPhase;
+
+export interface WebVitals {
+  lcp?: number; // Largest Contentful Paint
+  inp?: number; // Interaction to Next Paint
+  cls?: number; // Cumulative Layout Shift
+  fcp?: number; // First Contentful Paint
+  ttfb?: number; // Time to First Byte
+}
+
+export interface ScenarioConfig<TPhase extends string = MetricPhase> {
+  requiredPhases: TPhase[];
+  timeoutMs: number;
+  validate?: (ctx: ScenarioContextSnapshot<TPhase>) => boolean; // Optional custom validation
+}
+
+export interface PhaseTimings {
+  endTimeISO: string; // When the phase completed
+  durationMs: number; // Duration from scenario start to phase completion
+}
+
+export interface ScenarioContextSnapshot<TPhase extends string = MetricPhase> {
+  scenario: MetricScenario;
+  startTimeISO: string; // Human-readable ISO timestamp
+  endTimeISO: string; // Human-readable end timestamp
+  durationMs: number; // Total scenario duration from start to end
+  completed: TPhase[]; // Array for JSON serialization
+  failedPhases?: TPhase[]; // Phases that failed
+  timedOut: boolean;
+  vitals?: WebVitals;
+  phaseTimings?: Record<string, PhaseTimings>; // Start/end times for each phase
+}