V8: Use mculture in content editor for multilingual content

[kjac]

Prerequisites

• I have added steps to test this contribution in the description below

If there's an existing issue for this PR then this fixes #6022

Description

Looks like 88d9e33 introduced a bit of weird behavior for multilingual content; the selected main culture (mculture) is never applied to content when browsing around, thus unless cculture is explicitly specified, content is by default displayed in the default language no matter what is selected as main culture.

Here's a GIF that demonstrates the problem:

This PR fixes it by reverting this change from 88d9e33. When the PR is applied, the content editor once again conforms to the selected main culture:

Stuff to test

1. Verify that the selected main culture is displayed by default when browsing content - both when using the default and a non-default culture.
2. Verify that you can override the displayed culture on a per-content basis by selecting another culture in the language dropdown next to the content name.

[bjarnef]

There are a few examples of this syntax in the code from this PR #4955 😁

[nul800sebastiaan]

Nice one! 🎖