feat: add gotmpl file ext when using helmfile.d feature (#649)

Closes #654

Signed-off-by: yxxhero <aiopsclub@163.com>
Co-authored-by: Yusuke Kuoka <ykuoka@gmail.com>

pkg/app/testdata/app_list_test/default_environment_includes_all_releases

@@ -1,3 +1,4 @@
+found 3 helmfile state files in helmfile.d: /path/to/helmfile.d/helmfile_1.yaml, /path/to/helmfile.d/helmfile_2.yaml, /path/to/helmfile.d/helmfile_3.yaml
 processing file "helmfile_1.yaml" in directory "/path/to/helmfile.d"
 changing working directory to "/path/to/helmfile.d"
 first-pass rendering starting for "helmfile_1.yaml.part.0": inherited=&{default map[] map[]}, overrode=<nil>

pkg/app/testdata/app_list_test/fail_on_unknown_environment

@@ -1,3 +1,4 @@
+found 3 helmfile state files in helmfile.d: /path/to/helmfile.d/helmfile_1.yaml, /path/to/helmfile.d/helmfile_2.yaml, /path/to/helmfile.d/helmfile_3.yaml
 processing file "helmfile_1.yaml" in directory "/path/to/helmfile.d"
 changing working directory to "/path/to/helmfile.d"
 first-pass rendering starting for "helmfile_1.yaml.part.0": inherited=&{staging map[] map[]}, overrode=<nil>

pkg/app/testdata/app_list_test/filters_releases_for_environment_used_in_multiple_files

@@ -1,3 +1,4 @@
+found 3 helmfile state files in helmfile.d: /path/to/helmfile.d/helmfile_1.yaml, /path/to/helmfile.d/helmfile_2.yaml, /path/to/helmfile.d/helmfile_3.yaml
 processing file "helmfile_1.yaml" in directory "/path/to/helmfile.d"
 changing working directory to "/path/to/helmfile.d"
 first-pass rendering starting for "helmfile_1.yaml.part.0": inherited=&{shared map[] map[]}, overrode=<nil>

pkg/app/testdata/app_list_test/filters_releases_for_environment_used_in_one_file_only

@@ -1,3 +1,4 @@
+found 3 helmfile state files in helmfile.d: /path/to/helmfile.d/helmfile_1.yaml, /path/to/helmfile.d/helmfile_2.yaml, /path/to/helmfile.d/helmfile_3.yaml
 processing file "helmfile_1.yaml" in directory "/path/to/helmfile.d"
 changing working directory to "/path/to/helmfile.d"
 first-pass rendering starting for "helmfile_1.yaml.part.0": inherited=&{test map[] map[]}, overrode=<nil>

pkg/app/testdata/app_list_test/list_releases_matching_selector_and_environment

@@ -1,3 +1,4 @@
+found 3 helmfile state files in helmfile.d: /path/to/helmfile.d/helmfile_1.yaml, /path/to/helmfile.d/helmfile_2.yaml, /path/to/helmfile.d/helmfile_3.yaml
 processing file "helmfile_1.yaml" in directory "/path/to/helmfile.d"
 changing working directory to "/path/to/helmfile.d"
 first-pass rendering starting for "helmfile_1.yaml.part.0": inherited=&{development map[] map[]}, overrode=<nil>