Expose values of certain task manager configuration settings in the telemetry (elastic#202511)

In this PR, I'm adding some settings to the `exposeToUsage` variable
which allows the values of these settings to be reported via telemetry.
This way we can see what values, ratios, etc a certain setting has.

Settings to report values instead of `[redacted]`:
- `xpack.task_manager.claim_strategy`
- `xpack.task_manager.discovery.active_nodes_lookback`
- `xpack.task_manager.unsafe.exclude_task_types`

Author: mikecote

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

@@ -104,4 +104,13 @@ export const config: PluginConfigDescriptor<TaskManagerConfig> = {
       },
     ];
   },
+  exposeToUsage: {
+    claim_strategy: true,
+    discovery: {
+      active_nodes_lookback: true,
+    },
+    unsafe: {
+      exclude_task_types: true,
+    },
+  },
 };