Cleanup legacy code from `static/geonode` folder

[Gpetrak]

The static/geonode folder contains a significant amount of legacy code, including templates, JavaScript/CSS files, and images, which may no longer be in use and could be removed.

Proposed steps:

• Investigate and identify unused libraries and assets within the /static/geonode directory
• Clean up the identified legacy code from the folder
• Testing

[Gpetrak]

@giohappy @mattiagiupponi The PR for this issue is available here: #13201
The PR is aligned to add its commits in the branch of the previous issue #13199 because it's an extension of it.

Please keep in mind that two large libraries: ol-2.13 and proj4js included in the folder static/geonode/js can be removed but I didn't remove them yet because they are used in the geonode/client/tempates/ol templates.
These templates are also outdated but I prefer (after the issues related with static cleanup) to create a separate issue for removing outdated templates and I can remove these libraries in this issue.
For any concerns, please let me know.