Nuvoton: Add 'sectors' configuration option into targets.json

This change adds 'sectors' configuration option into 'targets.json' to enable bootloader for Nuvoton targets.
Though 'arm_pack_manager/index.json' has `sectors` available, Nuvoton's cmsis pack 'Nuvoton.NuMicro_DFP.pdsc' doesn't have 'sectors' entries and they must add into `index.json` manually. But not apply to all chip subfamilies.
To support custom board which uses a different chip subfamily, add 'secotors' into 'targets.json' for all Nuvoton targets which enable Flash IAP.

Author: ccli8

targets/targets.json

@@ -11815,6 +11815,12 @@
         "release_versions": [
             "5"
         ],
+        "sectors": [
+            [
+                0,
+                2048
+            ]
+        ],
         "device_name": "NUC472HI8AE",
         "bootloader_supported": true,
         "overrides": {
@@ -11982,6 +11988,12 @@
             "2",
             "5"
         ],
+        "sectors": [
+            [
+                0,
+                2048
+            ]
+        ],
         "device_name": "M453VG6AE",
         "bootloader_supported": true,
         "overrides": {
@@ -12836,6 +12848,12 @@
         "release_versions": [
             "5"
         ],
+        "sectors": [
+            [
+                0,
+                4096
+            ]
+        ],
         "bootloader_supported": true,
         "overrides": {
             "deep-sleep-latency": 1,
@@ -13221,6 +13239,12 @@
         "release_versions": [
             "5"
         ],
+        "sectors": [
+            [
+                0,
+                2048
+            ]
+        ],
         "bootloader_supported": true,
         "forced_reset_timeout": 3
     },
@@ -14892,6 +14916,12 @@
         "release_versions": [
             "5"
         ],
+        "sectors": [
+            [
+                0,
+                2048
+            ]
+        ],
         "bootloader_supported": true,
         "overrides": {
             "deep-sleep-latency": 1,