Rename board from ews_board to ews and fix board discovery

- Rename board directory: ews_board -> ews
- Rename board files: ews_board.dts -> ews.dts, ews_board_defconfig -> ews_defconfig
- Update board identifier and compatible strings
- Add board.cmake for runner configuration
- Set BOARD_ROOT in CMakeLists.txt to enable custom board discovery
- Update all documentation with new board name: west build -b ews

firmware/canfd_cdc_composite/boards/arm/ews/board.yml

@@ -0,0 +1,10 @@
+identifier: ews
+name: EWS Board
+type: mcu
+arch: arm
+family: stm32
+series: stm32g0x
+socs:
+  - name: stm32g0b1xx
+testing:
+  default: true