[N64] Save states: parallel-rdp state is not serialized

**Describe the bug** When saving and loading save states, the state of the rdp inside parallel-rdp is not saved and restored. This causes random "rdp crashes" due to invalid configuration states that would not have happened without a save state having been used. **To Reproduce** I made a test rom to exhibit the bug source: <https://github.com/Dragorn421/n64homebrew/blob/main/test_rdp_state/main.c> zip with the rom: https://github.com/user-attachments/files/27053999/test_rdp_state.zip 1) Expected behavior: Press A and observe in stdout that the green-filled texture is correctly blitted onto the red offscreen buffer 2) Make a save state 3) Load the save state 4) Press A 5) Observe a "rdp crash" instead **Additional context** ares discord: https://discord.com/channels/976404869386747954/976463759935696977/1496996116133056582 to https://discord.com/channels/976404869386747954/976463759935696977/1497225260628443307