cli: add basic probe-rs support

OpenOCD can be somewhat outdated. `probe-rs` is a more modern tool
written in Rust with many interesting features, like built-in RTT
logging support.

This commit just adds basic support, to be able to flash devices with
probe-rs and debug them.

targets/stm32l0x1.json

@@ -13,6 +13,7 @@
         "src/device/stm32/stm32l0x1.s"
     ],
     "flash-method": "openocd",
+    "probe-rs-chip": "STM32L031G6Ux",
     "openocd-interface": "cmsis-dap",
     "openocd-target": "stm32l0"
 }