[YUNIKORN-2159] Clean up AppManager implementation (#728)

Refactoring of AppManager implementations to consolidate into AppManagementService.

- Merged general app manager into AppManagementService
- Migrated pkg/appmgmt -> pkg/cache
- Migrated pkg/callback -> pkg/cache
- Migrated various utils -> pkg/cache to avoid circular dependencies
- Removed Recoverable interface (functionality merged into
  AppManagementService)
- Removed AppManager interface (functionality merged into
  AppManagementService)
- Removed ManagedApp and ManagedTask interfaces
- Skipped (currently) broken recovery tests due to interfaces not being usable.
  These tests will be rewritten in a future PR once the recovery code is integrated
  into the context.

Closes: #728

pkg/appmgmt/interfaces/amprotocol.go → pkg/cache/amprotocol.go

@@ -16,7 +16,7 @@
  limitations under the License.
 */
 
-package interfaces
+package cache
 
 import (
 	v1 "k8s.io/api/core/v1"
@@ -29,20 +29,20 @@ import (
 type ApplicationManagementProtocol interface {
 	// returns app that already existed in the cache,
 	// or nil, false if app with the given appID is not found
-	GetApplication(appID string) ManagedApp
+	GetApplication(appID string) *Application
 
 	// add app to the context, app manager needs to provide all
 	// necessary app metadata through this call. If this a existing app
 	// for recovery, the AddApplicationRequest#Recovery must be true.
-	AddApplication(request *AddApplicationRequest) ManagedApp
+	AddApplication(request *AddApplicationRequest) *Application
 
 	// remove application from the context
 	// returns an error if for some reason the app cannot be removed,
 	// e.g the given app is not found in current context.
 	RemoveApplication(appID string) error
 
 	// add task to the context, if add is successful,
-	AddTask(request *AddTaskRequest) ManagedTask
+	AddTask(request *AddTaskRequest) *Task
 
 	// remove task from the app
 	// return an error if for some reason the task cannot be removed