Bulk actions makes false assumption that ids will always be a number

[lb-]

Issue Summary

• Wagtail 2.15 brought in a new feature, bulk actions, for Page, User, Image and Document models however the current JavaScript assumes that the model object.id will be a number.
• https://docs.wagtail.org/en/stable/releases/2.15.html#bulk-actions

Steps to Reproduce

1. Start a new project with wagtail start mysite & then cd into folder
2. Run python manage.py startapp users
3. Add to file users/models.py

import uuid
from django.contrib.auth.models import AbstractUser
from django.db import models

class UserProfile(AbstractUser):
    id = models.UUIDField(primary_key=True, default=uuid.uuid4)

4. Update settings.py AUTH_USER_MODEL = 'users.UserProfile'
5. Run pip install -r requirements.txt (update to Wagtail 3.0 in requirements if needed)
6. Run python manage.py makemigrations and then python manage.py migrate
7. python manage.py createsuperuser
8. python manage.py runserver 0:8000
9. Now go to the users section (signed in as the superuser) and create a new user
10. On the user listing, manually select each one (but not the header checklist)
    11a. Expected: It should behave the same way as the other bulk actions when all items are manually selected and select the 'header' checkbox and the 'select all' checked in the footer bulk actions bar.
    11b. Actual: When manually selecting all it does not correctly auto-tick the all selected checkbox.
11. Expected: now, hard refresh the page and then click the 'select all' checkbox in the header, then when un-checking one item it should still show the bottom bar as if one is still selected
    12b. Actual: the bottom bar hide as if nothing was selected.

Any other relevant information. For example, why do you consider this a bug and what did you expect to happen instead?

• I have confirmed that this issue can be reproduced as described on a fresh Wagtail project: (yes)

Technical details

• Python version: Run 3.9.7
• Django version: 4.0.2
• Wagtail version: 3.0
• Browser version: Firefox 99

Root cause

• https://github.com/wagtail/wagtail/blob/main/client/src/entrypoints/admin/bulk-actions.js#L85
• https://github.com/wagtail/wagtail/blob/main/client/src/entrypoints/admin/bulk-actions.js#L91
• Using Number(e.target.dataset.objectId) will convert a non-number to NaN

Screenshots

Screenshot - manually select each item, not showing as 'all selected'

Screenshot - click select all and manually unselect one item - showing in broken state

Screenshot - user object id as uuid (not a normal number)