Resolve #3339161 "Implement hookhelp"

Closes #3339161

config/schema/menu_block_settings_override.schema.yml

+menu_block_setings_override.settings:
+  type: mapping
+  label: 'Menu block settings override - settings'
+  mapping:
+    blocks_enabled:
+      type: sequence
+      sequence:
+        type: string
+      label: 'Blocks IDs to enable the overrides for'
+    hidden_settings:
+      type: sequence
+      sequence:
+        type: string
+      label: 'Menu block setting names to hide on the per-page settings'