iOS 15 deprecation warnings: UIButtonConfiguration

[koke]

After merging #7851, which drops support for iOS 14, there are a few new warnings related to the new way of styling UIButton (see wwdc21-10064).

Xcode will complain when trying to set contentEdgeInsets, titleEdgeInsets, imageEdgeInsets directly.

We should be using UIButtonConfiguration instead, which might also simplify how we apply our common styles to buttons.

[peril-woocommerce]

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[iamgabrielma]

Fixed some warnings via #8094 and #8129

This surfaces a temporary problem at the moment, if we apply the UIButton configuration to the UIButtons+Helpers class we override the previous pink override for button colors, interestingly enough, this seems to be where we're actually heading as per pecCkj-fa-p2

In order to avoid double work, I'm holding a bit to see what's the direction we're taking before wrapping up the warning fixes.

[mokagio]

I came to the issues pages to open one about this, which I noticed while addressing #8326.

For discoverability, here's the full compiler warning text:

'contentEdgeInsets' was deprecated in iOS 15.0: This property is ignored when using UIButtonConfiguration