oidc: add regression tests for token claim json

this helps to verify that the same JSON is produced,
after these types are refactored.

pkg/oidc/regression_data/oidc.jwtProfileAssertion.json

@@ -0,0 +1,11 @@
+{
+	"aud": [
+		"foo",
+		"bar"
+	],
+	"exp": 12345,
+	"foo": "bar",
+	"iat": 12000,
+	"iss": "zitadel",
+	"sub": "hello@me.com"
+}