fix(kconfig): use 'n' instead of '0'/'false' for bool defaults

Bool symbols in nimble, BTDM, and two examples used invalid default
literals. The parser already falls back to 'n'; set that explicitly.

Co-authored-by: Cursor <cursoragent@cursor.com>

examples/peripherals/twai/twai_utils/main/Kconfig.projbuild

@@ -6,7 +6,7 @@ menu "TWAI Configuration"
     config EXAMPLE_ENABLE_TWAI_FD
         bool "Enable TWAI-FD Support"
         depends on SOC_TWAI_FD_SUPPORTED
-        default false
+        default n
         help
             Enable TWAI-FD (Flexible Data-rate) support.
             Allows up to 64 bytes of data per frame and dual bit rates.