nir/algebraic: Do better error reporting of bad expressions

nir/algebraic: Do better error reporting of bad expressions

Previously, if an exception was encountered anywhere, nir_algebraic would
just die in a fire with no indication whatsoever as to where the actual bug
is.  This commit makes it print out the particular search-and-replace
expression that is causing problems along with the exception.  Also, it
will now report all of the errors it finds and then exit at the end like a
standard C compiler would do.

Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>