test: add regression tests for #27468 (invalid URI segfaults)

Prior to PR #27468 (commit 11422cc) all
call-sites of `GetQueryParameter(...)` in the REST module could trigger
a crash. Add missing test cases for all possible code-paths as a
regression test, as a foundation for possible follow-up fixes (which aim
to resolve this issue in a more general and robust way).

Author: theStack

test/functional/interface_rest.py

@@ -278,8 +278,9 @@ def run_test(self):
         assert_equal(json_obj[0]['hash'], bb_hash)  # request/response hash should be the same
 
         # Check invalid uri (% symbol at the end of the request)
-        resp = self.test_rest_request(f"/headers/{bb_hash}%", ret_type=RetType.OBJ, status=400)
-        assert_equal(resp.read().decode('utf-8').rstrip(), "URI parsing failed, it likely contained RFC 3986 invalid characters")
+        for invalid_uri in [f"/headers/{bb_hash}%", f"/blockfilterheaders/basic/{bb_hash}%", "/mempool/contents.json?%"]:
+            resp = self.test_rest_request(invalid_uri, ret_type=RetType.OBJ, status=400)
+            assert_equal(resp.read().decode('utf-8').rstrip(), "URI parsing failed, it likely contained RFC 3986 invalid characters")
 
         # Compare with normal RPC block response
         rpc_block_json = self.nodes[0].getblock(bb_hash)