feat: add helmfile unittest command for helm-unittest integration (#2400)

Adds a new `helmfile unittest` command that integrates the helm-unittest
plugin, allowing users to define unit test paths per release and run them
via helmfile.

Closes #2376

Signed-off-by: Aditya Menon <amenon@canarytechnologies.com>

pkg/app/testdata/app_unittest_test/bad_selector

@@ -0,0 +1,6 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+0 release(s) matching app=test_non_existent found in helmfile.yaml
+
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/include-needs

@@ -0,0 +1,17 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+2 release(s) matching app=test found in helmfile.yaml
+
+processing 4 groups of releases in this order:
+GROUP RELEASES
+1     default/kube-system/logging
+2     default/kube-system/kubernetes-external-secrets
+3     default/default/external-secrets
+4     default/default/my-release
+
+processing releases in group 1/4: default/kube-system/logging
+processing releases in group 2/4: default/kube-system/kubernetes-external-secrets
+processing releases in group 3/4: default/default/external-secrets
+processing releases in group 4/4: default/default/my-release
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/release_without_unittests_is_skipped

@@ -0,0 +1,11 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+1 release(s) matching name=no-tests found in helmfile.yaml
+
+processing 1 groups of releases in this order:
+GROUP RELEASES
+1     default/default/no-tests
+
+processing releases in group 1/1: default/default/no-tests
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/skip-needs

@@ -0,0 +1,13 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+2 release(s) matching app=test found in helmfile.yaml
+
+processing 2 groups of releases in this order:
+GROUP RELEASES
+1     default/default/external-secrets
+2     default/default/my-release
+
+processing releases in group 1/2: default/default/external-secrets
+processing releases in group 2/2: default/default/my-release
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/unittest_all_releases_with_unittests

@@ -0,0 +1,17 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+5 release(s) found in helmfile.yaml
+
+processing 4 groups of releases in this order:
+GROUP RELEASES
+1     default/kube-system/logging, default/default/no-tests
+2     default/kube-system/kubernetes-external-secrets
+3     default/default/external-secrets
+4     default/default/my-release
+
+processing releases in group 1/4: default/kube-system/logging, default/default/no-tests
+processing releases in group 2/4: default/kube-system/kubernetes-external-secrets
+processing releases in group 3/4: default/default/external-secrets
+processing releases in group 4/4: default/default/my-release
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/with_dedicated_flags

@@ -0,0 +1,11 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+1 release(s) matching name=logging found in helmfile.yaml
+
+processing 1 groups of releases in this order:
+GROUP RELEASES
+1     default/kube-system/logging
+
+processing releases in group 1/1: default/kube-system/logging
+changing working directory back to "/path/to"

pkg/app/testdata/app_unittest_test/with_dedicated_flags_helm4

@@ -0,0 +1,13 @@
+processing file "helmfile.yaml" in directory "."
+changing working directory to "/path/to"
+merged environment: &{default  map[] map[] map[]}
+1 release(s) matching name=logging found in helmfile.yaml
+
+processing 1 groups of releases in this order:
+GROUP RELEASES
+1     default/kube-system/logging
+
+processing releases in group 1/1: default/kube-system/logging
+warn: --color flag is not supported with Helm 4 due to flag parsing issues, ignoring
+
+changing working directory back to "/path/to"