Extraneous space inserted after trailing comma

In many places Zeek allows trailing commas. This seems to be handled inconsistently.

For enums I see expected behavior:

type E: enum { a, b, c, };

For set-like constructs I see an additional space:

const s = { 1, 2, 3,  };
#                    ^

const r: RecordType = [ $a=1, $b=2, $c=3,  ];
#                                         ^

We probably have the same issue for function-like constructors, e.g.,

const a = vector(1, 2, 3, );
#                        ^

The issue seems to be that we insert an space after , in the contexts even though it is not followed by more arguments.

Start by locating the formatter entry points for enum, set-like, record, and vector constructs, then inspect how trailing commas are rendered. Reproduce the examples from the issue and compare each output with the enum behavior. Done means trailing commas are preserved without an extra space when no following argument exists, with coverage for the listed constructs.