[WCiOS17] Address warnings from WordPressAuthenticator deprecations

[iamgabrielma]

Closes WOOMOB-1796

Description

This PR addresses the titleEdgeInsets and setTitleEdgeInsets deprecation warnings coming from WordPressAuthenticator, by making WPNUXSecondaryButton use the new UIButtonConfiguration API instead.

We also remove other bits that throw warnings but are unused in the WCiOS codebase: WPNUXSecondaryButton, and WPWalkthroughOverlayView. Why? Since these are no longer maintained as part of the WordPressAuthenticator library, are now part of the WCiOS codebase and represent a maintenance burden for us, so let's get rid of them if unused.

Test Steps

Tagging kiwi for review as you know this flow better. AFAIK WPNUXSecondaryButtonTitleEdgeInsets is only used for the "forgot password" button in LoginSelfHostedViewController and LoginUsernamePasswordViewController, so these should look the same as before.

I've checked the connection flow through Menu > Select Store as well, but I think is not used there.

Screenshots

• Before and after:

[dangermattic]

	1 Warning
⚠️	This PR is larger than 300 lines of changes. Please consider splitting it into smaller PRs for easier and faster reviews.

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[wpmobilebot]

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

	App Name	WooCommerce iOS Prototype
	Build Number	pr16391-d70d12c
	Version	23.7
	Bundle ID	com.automattic.alpha.woocommerce
	Commit	d70d12c
	Installation URL	6t1pgskrv4js8

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[RafaelKayumov]

The change and cleanup look good and reasonable to me.

The WPNUXSecondaryButton is only used in LoginUsernamePasswordViewController and LoginSelfHostedViewController. But looks like those VC's are only presented in the legacy flow and seem to be unreachable in current flows.

I think we should investigate if those view controllers can be removed including the WPNUXSecondaryButton I wish I was more fluent with authorization flows. I'll approve the change and create a backlog issue for the investigation.

GPT 5.1 Codex analysis

The only code that still instantiates LoginUsernamePasswordViewController or LoginSelfHostedViewController lives in the legacy login stack (LoginSiteAddressViewController, LoginEmailViewController). In the shipping WooCommerce app we now drive everything through Unified Auth:
Entry screen is SiteAddressViewController (Unified Auth). When the delegate asks for password entry, it either shows SiteCredentialsViewController (self-hosted) or GetStartedViewController/email login for WP.com sites.
The delegate (AuthenticationManager) never requests presentPasswordController(isSelfHosted: false), so showWPUsernamePassword() is effectively dead code. Likewise, Unified Auth replaces LoginSelfHostedViewController with SiteCredentialsViewController.
So, in the current app build there is no live navigation path to either LoginUsernamePasswordViewController or LoginSelfHostedViewController; they’re leftovers from the pre–Unified Auth flow.

[iamgabrielma]

Thanks for the review!

The WPNUXSecondaryButton is only used in LoginUsernamePasswordViewController and LoginSelfHostedViewController. But looks like those VC's are only presented in the legacy flow and seem to be unreachable in current flows.
I think we should investigate if those view controllers can be removed including the WPNUXSecondaryButton I wish I was more fluent with authorization flows. I'll approve the change and create a backlog issue for the investigation.

Agree, I think there's a bunch of stuff that can be removed or cleaned up from the auth flows, but I haven't worked on those to know better and wanted to be careful. Thanks for logging a followup!