ci(sdspi): clean up newlib memory, reset between tests

Two changes to make the tests less susceptible to random failures:
- Free up newlib memory to not have false-positive memory leaks due to
  lazy allocations in reent structure
- Reset between tests, so that one failing test doesn't cause
  subsequent tests to fail

Both changes are already applied to esp_driver_sdmmc test app.

components/esp_driver_sdspi/test_apps/sdspi/pytest_sdspi.py

@@ -10,4 +10,4 @@ from pytest_embedded_idf import IdfDut
 @pytest.mark.esp32p4
 @pytest.mark.sdcard_spimode
 def test_sdspi(dut: IdfDut) -> None:
-    dut.run_all_single_board_cases()
+    dut.run_all_single_board_cases(reset=True)