Resolve "Elements with non-unique id on on projects new"

What does this MR do?

The project form on /projects/new is rendered four times on /projects/new. This PR adds a namespace to each form so that the element ids are unique again. I tried to keep the functionality the same. Where id selectors were ambiguous (e.g. #project_new) I used the corresponding id selector for a blank project. Where context was needed (e.g. generic id element within a tab) I introduced a new js- selector class.

Following nested form elements have their id now prefixed with #blank_project_, #template_project_, #import_url_. Need to check and update references in js/css.

• #project_ci_cd_only
• #new_project
• #project_name
• #project_namespace_id (hidden)
• #project_path
• #project_description
• #project_visibility_level_n
• #project_import_url
• #project_use_custom_template
• #project_mirror

Background: An newer version of select2 refuses to work with multiple select elements that share the same id out of the box (#32100 (closed)).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Closes #200001 (closed)