fix(core): Resolve TypeScript strict mode and ES client API compatibility issues for v3.0.0

- Fix ES client v8+ API: use document/doc instead of body for index/update operations
- Add type assertions (as any) for ES client ILM, template, and search APIs
- Fix strict null checks with proper undefined handling (nullish coalescing)
- Fix MetricsCollector interface to match required method signatures
- Fix Logger.error signature compatibility in plugins
- Resolve TermsQuery type index signature conflict
- Remove sourceMap from tsconfig (handled by tsbuild with inlineSourceMap)

ts/core/observability/tracing.ts

@@ -311,10 +311,16 @@ export class InMemoryTracer implements Tracer {
     const parts = traceparent.split('-');
     if (parts.length !== 4) return null;
 
+    const traceId = parts[1];
+    const spanId = parts[2];
+    const flagsStr = parts[3];
+
+    if (!traceId || !spanId || !flagsStr) return null;
+
     return {
-      traceId: parts[1],
-      spanId: parts[2],
-      traceFlags: parseInt(parts[3], 16),
+      traceId,
+      spanId,
+      traceFlags: parseInt(flagsStr, 16),
     };
   }
 }