Alerting: Break dependency between state and image packages (#58381)

* Refactor state and manager to not depend directly on image interface

* Move generic errors to models package

* Move NotAvailableImageService to state as its only references are in state tests

* Move NoopImageService to state package

* Move mock to state package

* Fix linter error

* Fix comment styling

* Fix a couple added references introduced by rebase

* Empty commit to kick build

pkg/services/ngalert/state/image_mock.go

@@ -0,0 +1,51 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/grafana/grafana/pkg/services/ngalert/state (interfaces: ImageCapturer)
+
+// Package state is a generated GoMock package.
+package state
+
+import (
+	context "context"
+	reflect "reflect"
+
+	gomock "github.com/golang/mock/gomock"
+	models "github.com/grafana/grafana/pkg/services/ngalert/models"
+)
+
+// MockImageCapturer is a mock of ImageCapturer interface.
+type MockImageCapturer struct {
+	ctrl     *gomock.Controller
+	recorder *MockImageCapturerMockRecorder
+}
+
+// MockImageCapturerMockRecorder is the mock recorder for MockImageCapturer.
+type MockImageCapturerMockRecorder struct {
+	mock *MockImageCapturer
+}
+
+// NewMockImageCapturer creates a new mock instance.
+func NewMockImageCapturer(ctrl *gomock.Controller) *MockImageCapturer {
+	mock := &MockImageCapturer{ctrl: ctrl}
+	mock.recorder = &MockImageCapturerMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use.
+func (m *MockImageCapturer) EXPECT() *MockImageCapturerMockRecorder {
+	return m.recorder
+}
+
+// NewImage mocks base method.
+func (m *MockImageCapturer) NewImage(arg0 context.Context, arg1 *models.AlertRule) (*models.Image, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "NewImage", arg0, arg1)
+	ret0, _ := ret[0].(*models.Image)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// NewImage indicates an expected call of NewImage.
+func (mr *MockImageCapturerMockRecorder) NewImage(arg0, arg1 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "NewImage", reflect.TypeOf((*MockImageCapturer)(nil).NewImage), arg0, arg1)
+}