Factorization of NRF51 and NRF52 targets.

A new wbase target has been added (NRF5).
In this target, commonalities between 51 and 52 will be shared.

hal/targets.json

@@ -1102,7 +1102,7 @@
         "OVERRIDE_BOOTLOADER_FILENAME": "nrf51822_bootloader.hex",
         "macros": ["NRF51", "TARGET_NRF51822"],
         "MERGE_BOOTLOADER": false,
-        "extra_labels": ["NORDIC", "MCU_NRF51", "MCU_NRF51822"],
+        "extra_labels": ["NORDIC", "MCU_NRF51", "MCU_NRF51822", "NRF5"],
         "OUTPUT_EXT": "hex",
         "is_disk_virtual": true,
         "supported_toolchains": ["ARM", "GCC_ARM"],
@@ -1739,7 +1739,7 @@
         "inherits": ["Target"],
         "core": "Cortex-M4F",
         "macros": ["NRF52", "TARGET_NRF52832"],
-        "extra_labels": ["NORDIC", "MCU_NRF52", "MCU_NRF52832"],
+        "extra_labels": ["NORDIC", "MCU_NRF52", "MCU_NRF52832", "NRF5"],
         "OUTPUT_EXT": "hex",
         "is_disk_virtual": true,
         "supported_toolchains": ["ARM", "GCC_ARM"],