Moving cropper action buttons to the bottom of the screen

[etoledom]

Closes #408

Description

Moving the action buttons from the navigation bar to a toolbar at the bottom of the screen:

Testing Steps

• Run the UIKit demo app.
• Navigate to Image Cropper demo.
  • NOTE: This won't be available on the CI builds .
• Choose and crop an image.
  • Check that the action buttons are visible and they work as expected.

[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	1270
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-uikit.prototype-build
	Commit	144672ff4b93f5003508734d3824a4b559d6677b
	App Center Build	Gravatar SDK Demo - UIKit #140

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	1270
	Version	1.0
	Bundle ID	com.automattic.gravatar-sdk-demo-swiftui.prototype-build
	Commit	144672ff4b93f5003508734d3824a4b559d6677b
	App Center Build	Gravatar SDK Demo - SwiftUI #139

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