[Response Ops][Task Manager] Add bulk update function that directly u…

…pdates using the `esClient` (#191760)

Resolves #187704

## Summary

Creates a new `bulkPartialUpdate` function in the `task_store` class
that uses the ES client to perform bulk partial updates instead of the
Saved Objects client. Updates the update in the `mget` task claimer to
use this new function.

## To verify

Run this branch with the `xpack.task_manager.claim_strategy: 'mget'` and
ensure that all tasks are running as expected.

---------

Co-authored-by: kibanamachine <[email protected]>

x-pack/plugins/task_manager/server/task.ts

@@ -456,6 +456,10 @@ export interface ConcreteTaskInstance extends TaskInstance {
   partition?: number;
 }
 
+export type PartialConcreteTaskInstance = Partial<ConcreteTaskInstance> & {
+  id: ConcreteTaskInstance['id'];
+};
+
 export interface ConcreteTaskInstanceVersion {
   /** The _id of the the document (not the SO id) */
   esId: string;
@@ -490,3 +494,7 @@ export type SerializedConcreteTaskInstance = Omit<
   runAt: string;
   partition?: number;
 };
+
+export type PartialSerializedConcreteTaskInstance = Partial<SerializedConcreteTaskInstance> & {
+  id: SerializedConcreteTaskInstance['id'];
+};