feat!: allow beta testers to access courses early

[Agrendalath]

BREAKING CHANGE: This requires:

1. Setting COURSE_ABOUT_VISIBILITY_PERMISSION = 'see_about_page'.
2. Removing the course_experience.pre_start_access Waffle flag (if enabled).
3. Setting the catalog_visibility in all courses to about or both.

How to update catalog visibility for all courses

# IMPORTANT: Run this in the CMS shell.
from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
from openedx.core.lib.courses import get_course_by_id
from xmodule.modulestore.django import modulestore
from xmodule.modulestore import ModuleStoreEnum

keys = CourseOverview.get_all_course_keys()

for key in keys:
    print(key)
    course = get_course_by_id(key)
    course.catalog_visibility = "both"
    modulestore().update_item(course, ModuleStoreEnum.UserID.primitive_command)

[Agrendalath]

Merging this to move forward.