boards/arm/stm32: Add b-g474e-dpow1:ostest configuration.

* boards/arm/stm32/b-g474e-dpow1/configs/ostest/defconfig:

  New file. Compared to b-g474e-dpow1:nsh, it adds the following
  configs:

  +CONFIG_BUILTIN=y
  +CONFIG_NSH_BUILTIN_APPS=y
  +CONFIG_TESTING_OSTEST=y

  and, because ostest currently fails when priority inheritance is
  enabled, it removes the following configs:

  -CONFIG_PRIORITY_INHERITANCE=y
  -CONFIG_PTHREAD_MUTEX_DEFAULT_PRIO_INHERIT=y

boards/arm/stm32/b-g474e-dpow1/configs/ostest/defconfig

@@ -0,0 +1,43 @@
+#
+# This file is autogenerated: PLEASE DO NOT EDIT IT.
+#
+# You can use "make menuconfig" to make any modifications to the installed .config file.
+# You can then do "make savedefconfig" to generate a new defconfig file that includes your
+# modifications.
+#
+# CONFIG_ARCH_LEDS is not set
+# CONFIG_DISABLE_OS_API is not set
+CONFIG_ARCH="arm"
+CONFIG_ARCH_BOARD="b-g474e-dpow1"
+CONFIG_ARCH_BOARD_B_G474E_DPOW1=y
+CONFIG_ARCH_BUTTONS=y
+CONFIG_ARCH_CHIP="stm32"
+CONFIG_ARCH_CHIP_STM32=y
+CONFIG_ARCH_CHIP_STM32G474R=y
+CONFIG_ARCH_HIPRI_INTERRUPT=y
+CONFIG_ARCH_RAMVECTORS=y
+CONFIG_ARCH_STACKDUMP=y
+CONFIG_ARMV7M_LIBM=y
+CONFIG_ARMV7M_MEMCPY=y
+CONFIG_BUILTIN=y
+CONFIG_DEBUG_FEATURES=y
+CONFIG_DEBUG_SYMBOLS=y
+CONFIG_INIT_ENTRYPOINT="nsh_main"
+CONFIG_LIBM=y
+CONFIG_NSH_ARCHINIT=y
+CONFIG_NSH_BUILTIN_APPS=y
+CONFIG_NSH_FILEIOSIZE=512
+CONFIG_NSH_LINELEN=64
+CONFIG_NSH_READLINE=y
+CONFIG_RAM_SIZE=98304
+CONFIG_RAM_START=0x20000000
+CONFIG_RAW_BINARY=y
+CONFIG_SCHED_HPWORK=y
+CONFIG_SCHED_LPWORK=y
+CONFIG_SCHED_WAITPID=y
+CONFIG_STM32_USART3=y
+CONFIG_SYSTEM_NSH=y
+CONFIG_TESTING_OSTEST=y
+CONFIG_USART3_SERIAL_CONSOLE=y
+CONFIG_USERLED=y
+CONFIG_USERLED_LOWER=y