[Woo POS] Remove dashboard view model

[joshheald]

Closes: #14458

Description

This PR removes the POS Dashboard view model.

To do this, I made the connectivity banner view self-contained, relying on its connectivity observer directly. Additionally, I moved some flags used to control the display of the support modal and the exit POS confirmation modal, to @State variables on the dashboard view, with bindings where required by the floating controls view.

Testing information

Again, with this PR most of the functionality had previously been stripped out of the dashboard view model. The main areas to test are whether the support and exit POS modals still display and dismiss correctly, and to check that the no internet connection banner animates in and out as it should.

I've tested the full flow on an iPad Air running iOS 17.7.

Screenshots

remove-dashboard-view-model.mp4

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• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

Reviewer (or Author, in the case of optional code reviews):

Please make sure these conditions are met before approving the PR, or request changes if the PR needs improvement:

• The PR is small and has a clear, single focus, or a valid explanation is provided in the description. If needed, please request to split it into smaller PRs.
• Ensure Adequate Unit Test Coverage: The changes are reasonably covered by unit tests or an explanation is provided in the PR description.
• Manual Testing: The author listed all the tests they ran, including smoke tests when needed (e.g., for refactorings). The reviewer confirmed that the PR works as expected on all devices (phone/tablet) and no regressions are added.

[wpmobilebot]

📲 You can test the changes from this Pull Request in WooCommerce iOS by scanning the QR code below to install the corresponding build.

	App Name	WooCommerce iOS
	Build Number	pr14483-2e5b222
	Version	21.1
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	2e5b222
	App Center Build	WooCommerce - Prototype Builds #11729

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

Version 21.2 has now entered code-freeze, so the milestone of this PR has been updated to 21.3.

[staskus]

✅ Tested on iPad Air M2 18.1

• Support modal
• Connectivity notice
• Smoke test payment and order flow

[staskus]

👍 Given this state var is only used to reflect user selection within the dashboard to open the modal, I think using '@State + @Binding` is a good move. Rather than using a view model as an intermediary.