[Link Checker GUI] Improve link source column

[MizukiTemma]

Short description

This PR introduced the new design for the column "Where is the link/Wo steht der link" (old: Quelle) as suggsted in the design.

Proposed changes

• Rename the column from "Quelle" to "Wo steht der Link
• Add underline to the page title
• Add title in the preferred language, if the link is in a content of another language (smaller text, gray out)
• Remove if-else with show_source_link as it won't link to the content form anymore
• Remove object_translation_has_view_perm which was only used for show_source_link
• Do not truncate content name and remove chevrons
• Positions of link text and "where is the link" (old: source) columns are swapped as agreed here

Side effects

Faithfulness to issue description and design

Changes for cases that are not specifically mentioned:

• Link to the organization form if the link is in an organization, as there is no app page for organizations (permission check is omitted, as the form view protects by itsself from changes by users without permission)
• Use user language as fallback for default language (original language) if user is in the global link list or the region's default_language returns None

How to test

• Insert an Url in a page translation of default language
• See the page title shown in the list with underline and it links to the app page
• Insert the same Url in a translation of another language of the page
• See the page title in the default language
• Delete the link in the default language translation
• See the page title of the other language with the title of default language beneath

Resolved issues

Fixes: #4459

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Pull Request Review Guidelines

[m0ndra]

@MizukiTemma Things I found while checking the design (not sure some of it will be implemented in another issue):

• I still see English texts in my German version
• Actually the links in the "Where is the link" column should be opened in a new tab and get a respective icon next to the string. I am sorry I missed to specify this in the acceptance criteria and my design file was inconsistent (I only had the icons visible in one design, not all of them - thats my fault 🙏). At the moment, the links all open in the same tab which is a big interruption for the user. I added the missing acceptance criteria to the issue, so that Julian can see it for testing. And I also made my design file consistent, you can see the icons here.

[MizukiTemma]

@m0ndra

Thank you for review 😸
The following changes are applied:

• Remove tool tips
• Add external link icon next to content name
• Opne the link in a new tab
• Do not truncate content name and remove chevrons (I noticed now this change was in the design)

[seluianova]

nice design and nice implementation 👍

[hannaseithe]

Thank you very much for working on this issue! I have a few change requests below

[MizukiTemma]

@hannaseithe

Thank you for review 😸 The PR is updated according to your suggestions ✏️

[hannaseithe]

Thank you very much for working in my change requests. This looks good to me :)