Migrate BlueprintJS OverlayToaster Component

[chownces]

BlueprintJS v4 OverlayToaster uses the deprecated ReactDOM.render.

We are currently working around it with these temporary changes (f3c4d76).

BlueprintJS might only deprecate the usage of ReactDOM.render in v6.

This issue seeks to track the BlueprintJS updates and to remove the above workaround once the new BlueprintJS API is ready

[RichDom2185]

BlueprintJS v5.9+ supports this now. See palantir/blueprint#5212 (comment) for the solution.