Scope and purpose

When upgrading select2, I discovered that the subnet allocator does not work (in master). Clicking on a subnet does not open the subpanel, but throws the following error in the console:

{
    "name": "Error",
    "message": "An \"el\" undefined must exist in DOM"
}

The bug is due to an incompatiblity with Marionette 2.x, which requires jQuery 2.x to work as intended. However, this PR adds a workaround which adds some manual jQuery to bypass the rendering issues.

Further follow-up work should be done to either upgrade or replace Backbone Marionette with something else, and is described in #3691.

This PR fixes the issue, and subnet allocation should work again.

Contributor Checklist

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Hacker's guide to NAV.

• Added a changelog fragment for towncrier
• Added/amended tests for new/changed code
• Added/changed documentation
• Linted/formatted the code with ruff, easiest by using pre-commit
• Wrote the commit message so that the first line continues the sentence "If applied, this commit will ...", starts with a capital letter, does not end with punctuation and is 50 characters or less long. See https://cbea.ms/git-commit/
• Based this pull request on the correct upstream branch: For a patch/bugfix affecting the latest stable version, it should be based on that version's branch (<major>.<minor>.x). For a new feature or other additions, it should be based on master.
• If applicable: Created new issues if this PR does not fix the issue completely/there is further work to be done
• If it's not obvious from a linked issue, described how to interact with NAV in order for a reviewer to observe the effects of this change first-hand (commands, URLs, UI interactions)
• If this results in changes in the UI: Added screenshots of the before and after
• If this adds a new Python source code file: Added the boilerplate header to that file