[Admin] Create new Tax Categories

[spaghetticode]

This PR migrates the creation of new tax categories to the new admin interface. Because the tax category form now opens in a modal, we need to carry over the page and q parameters to maintain consistency in user experience.

Additionally, the PR resolves an issue with filtering on the tax categories list page, which was not functioning correctly.

Please refer to the attached video for a visual demo.

https://github.com/solidusio/solidus/assets/141220/7b0ddc96-b5c4-4344-bfa2-7b8160d598fa

Checklist

• [x] I have written a thorough PR description.
• [x] I have kept my commits small and atomic.
• [x] [I have used clear, explanatory commit messages]-
• [x] I have added automated tests to cover my changes.
• [x] I have attached screenshots to demo visual changes.

[kennyadsl]

As discussed during the core team meeting, I'd give turbo frame a go for this modal, which I have the feeling can be simplified.

[spaghetticode]

@kennyadsl I've just updated the PR and its description, video included. It's now leveraging Turbo frames and Turbo streams refreshes.

Spec failures are related to the latest release of the money gem (tags have not been pushed yet, so I'm not sure what change broke it), which seems to replace the EURO currency symbol from HTML entity (€) to unicode char (€). I'll open a PR with the fix later.

[spaghetticode]

I tracked down the money gem issue to this PR. The change is included in 6.18.0, but not in 6.17.0, both released today 🤷 .