Generate code that formats faster with "short" style.

[davidmorgan]

For #1335

Before:

dart format --language-version=3.6 */lib/*.g.dart
Formatted 20 files (0 changed) in 3.55 seconds.

After:

dart format --language-version=3.6 */lib/*.g.dart
Formatted 20 files (0 changed) in 1.01 seconds.

Note that the speedup is more than 3.5x as "dart format" has some startup time.

[iinozemtsev]

LG

[iinozemtsev]

so the trick is to proactively add a trailing comma?

[davidmorgan]

so the trick is to proactively add a trailing comma?

Right, that switches to the less-indented format that's more like the new "tall" style. And also turns out to be faster in this case :)