Add radio information for more aircraft.

Adds the following:

* AJS37
* AV-8B
* JF-17

This does move the preset channel allocation logic into its own class,
since we need to customize that behavior for the AJS37 since it has a
rather unique preset channel layout (see the comments in
`ViggenRadioChannelAllocator` for details).

gen/radios.py

@@ -116,6 +116,12 @@ RADIOS: List[Radio] = [
     # to 400 MHz range, but we can't model gaps with the current implementation.
     # https://www.heatblur.se/F-14Manual/general.html#an-arc-182-v-uhf-2-radio
     Radio("AN/ARC-182", MHz(108), MHz(174), step=MHz(1)),
+
+    # Also capable of [103, 156) at 25 kHz intervals, but we can't do gaps.
+    Radio("FR 22", MHz(225), MHz(400), step=kHz(50)),
+
+    Radio("R&S M3AR VHF", MHz(108), MHz(174), step=MHz(1)),
+    Radio("R&S M3AR UHF", MHz(225), MHz(400), step=MHz(1)),
 ]