Add XIAO Wio-SX1262 overlay; support SX12xx bandwidths (including 62.5 kHz) as default

- boards/seeed/xiao_wio_sx1262: add overlay, .conf, board.yml
- app: support full set of SX12xx bandwidths; default BW set to 62 (62.5 kHz)
- Update Kconfig and prj.conf
- Update lora_modem.h/c for validation and mapping

boards/lilygo/lilygo_tbeam/board.yml

@@ -2,7 +2,6 @@ board:
   name: lilygo_tbeam
   full_name: "LilyGo T-Beam"
   vendor: lilygo
-  url: https://www.lilygo.cc/products/t-beam-v1-1
   socs:
     - name: esp32
       variants: