with-columns should have escape hatch for capitalization

[seancorfield]

The current logic -- that always capitalizes all but the first expression in a column spec -- is somewhat problematic and has no way to specify a literal type that should not be capitalized (see #428 for examples).

The sql-kw function allows for keywords that start with ' to be passed through exactly as-is which supports function usage (and a few other things) but format-var does not support that. Perhaps it should?

[seancorfield]

In addition to format-var needing to support that escape hatch, with-columns itself needs to be adjusted so it doesn't then reformat such an expression, removing the (upper-case) call in some as yet unspecified situations.

[seancorfield]

Example:

user=> (-> (with-columns [:foo :'String] [:bar :int :'Not :quite :'Null :here]) (sql/format))
["(foo String, bar INT Not QUITE Null HERE)"]
user=>

I need to decide whether/where to document this since I think I deliberately left it undocumented when 2.2.868 was released.