Scope and purpose

This PR adds a new size option to modals, fit-content, which allows modals to grow as wide as they need.

As an example, this is necessary to support a wider "Add widget" modal on the dashboard, as demonstrated in #3487.
See provided screenshot for the effect this change would have.

This pull request

• Adds new modal size, fit-content, to support larger content
• Sets fit-content as default modal size (was tiny)
• Updates existing add/remove patch modals with explicit "tiny" size

Screenshots

With the new default (.fit-content), the "Add widget" modal would look like this:

Contributor Checklist

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More information about contributing to NAV can be found in the
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
• The first line of the commit message 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/
• This pull request is based 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 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