Bringing back old image upload method

[etoledom]

Closes #

Description

This PR continues the work on #492 and targets it.

• Bringing back old good upload(_:email: accessToken:) -> URLResponse, which uses the v1 upload endpoint
• Removing avatarSelection from the v3 image upload method.
• AvatarSelection is now internal.

upload(_:email: accessToken:) -> URLResponse
and
upload(_:accessToken:) -> AvatarType
use the v1 and v3 endpoints respectively.

Testing Steps

[wpmobilebot]

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

	App Name	Gravatar UIKit Prototype Build
	Build Number	1479
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-uikit.prototype-build
	Commit	4aab077
	App Center Build	Gravatar SDK Demo - UIKit #257

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

[wpmobilebot]

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

	App Name	Gravatar SwiftUI Prototype Build
	Build Number	1479
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-swiftui.prototype-build
	Commit	4aab077
	App Center Build	Gravatar SDK Demo - SwiftUI #257

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