* Add checks to prevent people from using negative split factors

Our analysis passes assume that loop maxes are greater than loop mins,
so negative split factors cause sufficient havoc that not even output
bounds queries are safe. These are therefore checked on pipeline entry.

This is a new way for output bounds queries to throw errors (in addition
to the buffer pointers themselves being null, and maybe some buffer
constraints). Testing this, I realized these errors were getting thrown
twice, because the output buffer bounds query in Pipeline::realize was
built around two recursive calls to realize, and both were calling the
custom error handler. In addition to reporting errors in this class
twice, this implies several other inefficiencies, e.g. jit call args
were being prepped twice. I reworked it to be built around two calls to
call_jit_code instead.

Fixes #7938

* Add test to cmakelists

* Remove pointless target arg to call_jit_code

It has to be the same as the cached target in the receiving object
anyway