This change makes it so that we no longer create 'design time' engines.
The choice of design time or runtime is made when we initiate a code
generation operation.
Options instances are now created as part of the CodeDocument
initialization. Our existing code can still be created using a
RazorEngine so our passes that initialize the options still support the
old code path.
- Renamed `IRazorParserOptionsFeature` to `IConfigureRazorParserOptionsFeature`, the original interface was re-purposed to get the options rather than configure them.
- This involved re-designing how we set design time on the `RazorParserOptions` object. The indicator of `DesignTime` is now configured at the RazorEngine level via a parser options provider feature.
- Moved options construction from the phase into an `IRazorParserOptionsFeature` type.
#1510