new problem and deleted the obsolete problem loader

src/problems/regex-phone/manifest.json

@@ -0,0 +1,7 @@
+{
+    "title": "Regex Phonenumber",
+    "description": "A regex problem to match phone numbers in various formats.",
+    "description_md": "problems/regex-phone/description.md",
+    "difficulty": "hard",
+    "test_code": "problems/regex-phone/test.py"
+}