Never consider vertical layout if a command can be put in one line

[guoang]

For example, This command:

set(SOME_VARIABLE "some value" CACHE STRING "some description")

will be formatted to

set(SOME_VARIABLE
    "some value"
    CACHE STRING "some description")

with config max_subgroups_hwrap = 2.

I think maybe we should keep a command in one line if it is shorter than line_width. This rule should have higher priority than any other hwrap rules. Or at least provide a config option to enable/disable this rule.