fix: Fix needs to work for upgrades and when selectors are provided (#922)

* fix: Fix `needs` to work for upgrades and when selectors are provided

Fixes #919

* Add test framework for `helmfile apply`

* Various enhancements and fixes to the DAG support

- Make the order of upgrades/deletes more deterministic for testability
- Fix the test framework so that we can validate log outputs and errors
- Add more test cases for `helmfile apply`, along with bug fixes.
- Make sure it fails with an intuitive error when you have non-existent releases referenced from witin "needs"

pkg/state/state_exec_tmpl_test.go

@@ -138,9 +138,9 @@ func TestHelmState_executeTemplates(t *testing.T) {
 				HelmDefaults: HelmSpec{
 					KubeContext: "test_context",
 				},
-				Env:          environment.Environment{Name: "test_env"},
-				Namespace:    "test-namespace_",
-				Repositories: nil,
+				Env:               environment.Environment{Name: "test_env"},
+				OverrideNamespace: "test-namespace_",
+				Repositories:      nil,
 				Releases: []ReleaseSpec{
 					tt.input,
 				},
@@ -238,9 +238,9 @@ func TestHelmState_recursiveRefsTemplates(t *testing.T) {
 				HelmDefaults: HelmSpec{
 					KubeContext: "test_context",
 				},
-				Env:          environment.Environment{Name: "test_env"},
-				Namespace:    "test-namespace_",
-				Repositories: nil,
+				Env:               environment.Environment{Name: "test_env"},
+				OverrideNamespace: "test-namespace_",
+				Repositories:      nil,
 				Releases: []ReleaseSpec{
 					tt.input,
 				},