[Kibana Search] Promote Observability Alerts higher in the global search (#241209)

Resolves #176678 

This PR adds keywords to the Observability Plugin deeplink to make
Alerts show higher in the global search when user is looking for
'Alerts'

---------

Co-authored-by: Bena Kansara <[email protected]>

Author: ana-davydova

x-pack/solutions/observability/plugins/observability/public/plugin.ts

@@ -215,6 +215,7 @@ export class Plugin
           visibleIn: [],
         },
       ],
+      keywords: ['alerts', 'rules'],
     },
   ];