BUG Don't double up the breadcrumb on list views

Description

This PR refactors how the CMS breadcrumb is generated.

It fix a bug causing crumbs to be duplicated on the list view.

It also ensures the "Pages" top crumb is always shown on the list view.

It adds missing unit tests.

Validate that the breadcrumb is still shown correctly:
- on the page edit form
- on the list view when access directly
- on the list view when access via a PJAX
- on the page search results.
Validate that crumbs link where you expect them to link.

[x] The target branch is correct
[x] All commits are relevant to the purpose of the PR (e.g. no debug statements, unrelated refactoring, or arbitrary linting)
[x] The commit messages follow our commit message guidelines
[x] The PR follows our contribution guidelines
[x] Code changes follow our coding conventions
[x] This change is covered with tests (or tests aren't necessary for this change)
[x] Any relevant User Help/Developer documentation is updated; for impactful changes, information is added to the changelog for the intended release
[x] CI is green