Remove unneeded parenthesis from type printing

[jfecher]

Currently while displaying types we show an unnecessary amount of parenthesis. This can be seen while printing error messages.

E.g. examples/typechecking/completeness_checking.an has the following as its last error message:

completeness_checking.an:25:4	error: This pattern of type ((Int a), (Int b)) does not match the type ((Int a), ((Int b), ((Int c), (Int d)))) that is being matched on
| (1, 2) -> 1

Ideally we would display the following instead:

completeness_checking.an:25:4	error: This pattern of type (Int a, Int b) does not match the type (Int a, (Int b, (Int c, Int d))) that is being matched on
| (1, 2) -> 1

Or even the following since , is right-associative:

completeness_checking.an:25:4	error: This pattern of type Int a, Int b does not match the type Int a, Int b, Int c, Int d that is being matched on
| (1, 2) -> 1

The file to change for this issue would be src/types/typeprinter.rs. I imagine instead of always parenthesizing certain types we'll want to never do so on the type itself, and only parenthesize on certain argument positions. Either by checking the type variant or a check like !type_string.contains_spaces().