`EnsureRenderedStringPattern` preprocessor should warn without rejecting strings containing verbatim directives

[mchalek]

Right now, if you have a parameter that uses the EnsureRenderedStringPattern pre-processor, and if you pass a verbatim string to this parameter, there is a chance that the parameter value will be rejected as invalid because the characters < and > are not supported by the provided regular expression. An example is the dataproc cluster_name parameter. We should recognize this condition and generate a warning, like we do when we encounter a jinja template that we do not know how to render.

[hyungoos]

Thanks for creating tracking this down!