We need to add @objc annotations to the containerScheme instances in our Swift examples, because we moved to Swift 4.2, the respondsToSelector won't find the setContainerScheme: setter otherwise.
This PR graduates ContainerScheme to ready.
This includes updating the podspecs, podfile, all the import statements related to ContainerScheme, updating .kokoro rewrite rules, and finally the readme to not have ContainerScheme regarded to as being in beta.
Ran locally kokoro with -b bazel successfully.
Resolves#6732
This is a follow up PR for #7166 adds @objc annotations to Swift catalogMetadata() methods, because the Swift 4 compiler no longer attempts to infer what methods should be visible to Objective-C. As a result of this change in the compiler, no Swift examples were showing up in Dragons after #7166. See this article: https://useyourloaf.com/blog/objc-warnings-upgrading-to-swift-4/ for additional context.
DialogPresentationController changes the corner radius dynamically during presentation while ensuring that the presented view's corner radius always matches the corner radius of the tracking view which draws the shadow behind the presented view.
## Introduction
Before we move container scheme to ready we need to have both the `colorScheme` and `typographyScheme` nonnull. By making colorScheme and typographyScheme of MDCContainerScheming nonnull, clients will reduce the amount of conditional checks required in their apps and reduce a category of potential errors (accidentally passing nil to a nonnull parameter).
## The problem
Both `colorScheme` and `typographyScheme` were nullable in the container scheme making it harder for clients to use the container scheme throughout their app on non Material UIElements, i.e. UIView.backgroundColor
## The fix
Make both of these properties nonnull.
## Additional work
- [x] I had to update the swift examples to not be optional and I additionally removed the nil checks from the ObjC examples.
## Related links
* Bug: #6438
* Component: [Dialogs](https://github.com/material-components/material-components-ios/tree/develop/components/Dialogs)
## Introduction
As we move to theming extensions all components that have a theming extension should use that within it's examples. Currently MDCAlertController has a theming extension and should use it in all examples. Additionally all components within the examples that have a theming extension should use it.
## The problem
Within MDCAlertController examples some components are using the old _Themers_.
## The fix
For all components being used in MDCAlertController examples use a theming extension if available.
## Additional notes
This also cleans up some ivar usage and import statements.
