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_tinygo.go

@@ -0,0 +1,37 @@
+//go:build baremetal
+
+package legacy
+
+import (
+	"machine"
+
+	"tinygo.org/x/drivers/internal/pin"
+)
+
+func configurePinOut(po pin.Output) {
+	configurePin(po, machine.PinOutput)
+}
+
+func configurePinInputPulldown(pi pin.Input) {
+	configurePin(pi, pulldown) // some chips do not have pull down, in which case pulldown==machine.PinInput.
+}
+
+func configurePinInput(pi pin.Input) {
+	configurePin(pi, machine.PinInput)
+}
+
+func configurePinInputPullup(pi pin.Input) {
+	configurePin(pi, pullup) // some chips do not have pull up, in which case pullup==machine.PinInput.
+}
+
+func pinIsNoPin(a any) bool {
+	p, ok := a.(machine.Pin)
+	return ok && p == machine.NoPin
+}
+
+func configurePin(p any, mode machine.PinMode) {
+	machinePin, ok := p.(machine.Pin)
+	if ok {
+		machinePin.Configure(machine.PinConfig{Mode: mode})
+	}
+}