Optimize function signature display with line break in hover preview.

[aprosail]

Optimize the function signature hover preview please, don't just display the raw code. Maybe we can process the whole function signature hover preview string into a single line, remove unnecessary line break and trailing commas according to zig syntax. Or, at least, format the indent to display it normally.

Most function signatures in zig source code are in a single line, but some of them are not. Once coding with longer function signatures which cannot be place into a single line, the hover preview will be like this, which is not pretty.

[Techatrix]

I have opened zigtools/zls#2107 which tracks this issue for the ZLS language server.