stm32: Remove OptionalPin

The idea behind OptionalPin has a few problems:

- you need to impl the signal traits for NoPin which is a bit weird https://github.com/embassy-rs/embassy/blob/master/embassy-stm32/src/dcmi.rs#L413-L416
- you can pass any combination of set/unset pins, which needs checking at runtime  https://github.com/embassy-rs/embassy/blob/master/embassy-stm32/src/dcmi.rs#L130

The replacement is to do multiple `new` constructors for each combination of pins you want to take.

embassy-stm32/src/subghz/mod.rs

@@ -215,11 +215,11 @@ impl<'d, Tx, Rx> SubGhz<'d, Tx, Rx> {
     /// clock.
     pub fn new(
         peri: impl Unborrow<Target = SUBGHZSPI> + 'd,
-        sck: impl Unborrow<Target = impl SckPin<SUBGHZSPI>>,
-        mosi: impl Unborrow<Target = impl MosiPin<SUBGHZSPI>>,
-        miso: impl Unborrow<Target = impl MisoPin<SUBGHZSPI>>,
-        txdma: impl Unborrow<Target = Tx>,
-        rxdma: impl Unborrow<Target = Rx>,
+        sck: impl Unborrow<Target = impl SckPin<SUBGHZSPI>> + 'd,
+        mosi: impl Unborrow<Target = impl MosiPin<SUBGHZSPI>> + 'd,
+        miso: impl Unborrow<Target = impl MisoPin<SUBGHZSPI>> + 'd,
+        txdma: impl Unborrow<Target = Tx> + 'd,
+        rxdma: impl Unborrow<Target = Rx> + 'd,
     ) -> Self {
         Self::pulse_radio_reset();