Fix release notes and updatemodulepaths to cover coreutils module rename (#8396)

Fixes #8376

docs/releases/3.0.md

@@ -134,7 +134,8 @@ When using a queryset to render a list of items with images, you can now make us
 
 Various modules of Wagtail have been reorganised, and imports should be updated as follows:
 
-* All modules under `wagtail.core` can now be found under `wagtail` - for example, `from wagtail.core.models import Page` should be changed to `from wagtail.models import Page`
+* The `wagtail.core.utils` module is renamed to `wagtail.coreutils`
+* All other modules under `wagtail.core` can now be found under `wagtail` - for example, `from wagtail.core.models import Page` should be changed to `from wagtail.models import Page`
 * The `wagtail.tests` module is renamed to `wagtail.test`
 * `wagtail.admin.edit_handlers` is renamed to `wagtail.admin.panels`
 * `wagtail.contrib.forms.edit_handlers` is renamed to `wagtail.contrib.forms.panels`

wagtail/bin/wagtail.py

@@ -152,6 +152,7 @@ class UpdateModulePaths(Command):
         ),
         # Added in Wagtail 3.0
         (re.compile(r"\bwagtail\.tests\b"), "wagtail.test"),
+        (re.compile(r"\bwagtail\.core\.utils\b"), "wagtail.coreutils"),
         (re.compile(r"\bwagtail\.core\b"), "wagtail"),
         (re.compile(r"\bwagtail\.admin\.edit_handlers\b"), "wagtail.admin.panels"),
         (