RP2040: add SPI PIO interface option, enhance 8 bit parallel PIO

The RP2040 processors can now drive 8 bit parallel and SPI displays using the PIO hardware.

The PIO offloads the processor by providing:
1. PIO managed setWindow sequence
2. PIO managed block and screen fill

Extensions/Sprite.cpp

@@ -37,6 +37,9 @@ TFT_eSprite::TFT_eSprite(TFT_eSPI *tft)
   _colorMap = nullptr;
 
   _psram_enable = true;
+  
+  // Ensure end_tft_write() does nothing in inherited functions.
+  lockTransaction = true;
 }