Replace deprecated ReactDOM methods in OverlayToaster

[ggdouglas]

Tracking work required for full compatibility with React 18. The OverlayToaster component exposes a synchronous OverlayToaster.create() static method that uses ReactDOM.render. The asynchronous OverlayToaster.createAsync method allows for an optional custom DOM renderer to be passed in (such as root.render), but also uses ReactDOM.render as the default. This issue is similar/related to #7165

blueprint/packages/core/src/components/toast/toast.md

Lines 187 to 206 in ee5510c

	#### React 18
	To maintain backwards compatibility with React 16 and 17, `OverlayToaster.createAsync` uses `ReactDOM.render` out of the box. This triggers a [console warning on React 18](https://react.dev/blog/2022/03/08/react-18-upgrade-guide#updates-to-client-rendering-apis).
	A future major version of Blueprint will drop support for React versions before 18 and switch the
	default rendering function from `ReactDOM.render` to `createRoot`.
	If you're using React 18, we recommend passing in a custom `domRenderer` function.
	```tsx
	import { OverlayToaster } from "@blueprintjs/core";
	import { createRoot } from "react-dom/client";
	const toaster = await OverlayToaster.createAsync(toasterProps, {
	// Use createRoot() instead of ReactDOM.render(). This can be deleted after
	// a future Blueprint version uses createRoot() for Toasters by default.
	domRenderer: (toaster, containerElement) => createRoot(containerElement).render(toaster),
	});
	toaster.show({ message: "Hello React 18!" });
	```

We should:

1. Remove/replace the synchronous OverlayToaster.create() method
2. Replace the DOMMountOptions defaults with root.render

Code:

overlayToaster.tsx
mountOptions.ts

blueprint/packages/core/src/components/toast/overlayToaster.tsx

Line 79 in ee5510c

const toaster = ReactDOM.render<OverlayToasterProps>(

blueprint/packages/core/src/components/toast/overlayToaster.tsx

Line 103 in ee5510c

const domRenderer = options?.domRenderer ?? ReactDOM.render;

blueprint/packages/core/src/components/toast/overlayToaster.tsx

Lines 89 to 96 in ee5510c

	/**
	* Similar to {@link OverlayToaster.create}, but returns a Promise to a
	* Toaster instance after it's rendered and mounted to the DOM.
	*
	* This API will replace the synchronous {@link OverlayToaster.create} in a
	* future major version of Blueprint to reflect React 18+'s new asynchronous
	* rendering API.
	*/

References:

1. https://react.dev/blog/2022/03/08/react-18-upgrade-guide#updates-to-client-rendering-apis
2. Replacing render with createRoot reactwg/react-18#5

[ggdouglas]

For the initial internal React 18 upgrade, these deprecations will need to be ignored to pass the linter: #7160