Deprecate resilient mode

Fastboot supports a `resilient` mode that allows one to swallow errors and not reject the promise if there are rendering errors. Often this can troll the consumers where they expect some output from fastboot but there was none *and* no error to indicate what is wrong. This issue is to open discussion whether we should deprecate `resilient` mode in future.

Alternatively, if we don't want to drop the support, we should atleast add warning when the promise is rejected that fastboot and return the error object as part of promise resolution. This will help consumers understand in more detail.