feat(tests): add test case for P256 with r max value (#2229)

This test uses the max value for the `r` element of the `p256verify`
precompile input. This is added for completeness only as there is no
practical way to generate a semi-valid signature with arbitrary `r`.

Author: chfast

tests/osaka/eip7951_p256verify_precompiles/test_p256verify.py

@@ -232,6 +232,10 @@ def test_valid(state_test: StateTestFiller, pre: Alloc, post: dict, tx: Transact
             Spec.H0 + R(Spec.N) + Spec.S0 + Spec.X0 + Spec.Y0,
             id="r_eq_to_n",
         ),
+        pytest.param(
+            Spec.H0 + R(2**256 - 1) + Spec.S0 + Spec.X0 + Spec.Y0,
+            id="r_max",
+        ),
         pytest.param(
             Spec.H0 + Spec.R0 + S(0) + Spec.X0 + Spec.Y0,
             id="s_eq_to_zero",