PinInput+PinOutput HAL (#753, reloaded) (#795)

* first commit: add HAL and uc8151 driver demo
* unexport drivers.PinOutput/Input HAL
* fix non-tinygo pin config build
* change of heart
* docs: corrected some comments that were not changed at the same time as recent renaming

internal/legacy/pinconfig_go.go

@@ -0,0 +1,15 @@
+//go:build !tinygo
+
+package legacy
+
+import "tinygo.org/x/drivers/internal/pin"
+
+// This file compiles for non-tinygo builds
+// for use with "big" or "upstream" Go where
+// there is no machine package.
+
+func configurePinOut(p pin.Output)          {}
+func configurePinInput(p pin.Input)         {}
+func configurePinInputPulldown(p pin.Input) {}
+func configurePinInputPullup(p pin.Input)   {}
+func pinIsNoPin(a any) bool                 { return false }