Limit Postgres MIN/MAX to an arity of one

[eygraber]

No description provided.

[eygraber]

Changes like this are going to make the compiler tests a little more difficult as-is because there might need to be different variants of tests for different dialects (e.g. max takes the proper type in ExpressionTest would need to account for sqlite allowing multiple arguments to MAX but other dialects limiting it to one argument).

Any thoughts on how to address that? I was originally thinking of having packages of tests for common behavior, and then individual ones for each dialect as needed. It can get clunky in cases where most dialects have one behavior (like with MAX), i.e. should each dialect have the same test, or put one test in the common package for the majority of the dialects and have other tests for specially behaving dialects as needed?

Edit: maybe that wasn't the best example since the tests aren't really needed for non sqlite dialects since they only operate on one argument, and those tests are related to picking the correct type when multiple arguments are passed.

[eygraber]

@hfhbd any thoughts on this approach?