My hunch is that code density is more important than avoiding
ome of the `if (rewrite_args)` checks.

Also add some hacks to get rid of the func-name-getter-as-lambda,
so we don't need to templatize on that either.

Results of this commit are kind of mixed:

       django_template3_10x.py            13.6s (2)            13.8s (2)  +1.4%
 sqlalchemy_imperative2_10x.py            18.8s (2)            19.0s (2)  +1.2%
            pyxl_bench2_10x.py            10.7s (2)            10.1s (2)  -5.1%
                       geomean                14.0s                13.8s  -0.9%