refactor: add conftest command into testing-image for refactoring e2e conftest ensure logic to upgrade conftest upgrading

[krrrr38]

what

• add conftest command in testing-image, not conftest$version command

why

Based on #2807 (comment) discussion, we want to remove e2e ocontroller version specific conftest command like

atlantis/server/controllers/events/events_controller_e2e_test.go

Lines 1366 to 1372 in 6a7f79e

	// Will fail test if conftest isn't in path and isn't version >= 0.25.0
	func ensureRunningConftest(t *testing.T) {
	localPath, err := exec.LookPath(fmt.Sprintf("conftest%s", ConftestVersion))
	if err != nil {
	t.Logf("conftest >= %s must be installed to run this test", ConftestVersion)
	t.FailNow()
	}

.

This version specific dependency is hard to upgrade conftest automatically.

To remove version dependency, I just add conftest comand. I will change e2e by using this command in the next PR.

references

• Prevent manual PRs to update TF and CONFTEST versions #2638
• feat: renovate handle regexManagers to update conftest/tf versions #2807 (comment)