Fix formatter lib-fun declaration with newlines

[ftarulla]

Fixes #12070

The formatter tool was crashing when trying to indent lib fun declarations with newlines.
For example:

lib Foo
  fun foo =
    bar : Void
end 

After this PR the formatter can handle such cases. Other example:

input:

lib Foo
  fun foo =


    bar : Void
end

output:

lib Foo
  fun foo =
    bar : Void
end

[straight-shoota]

This should also apply to cases where the function name is a string literal (which is handled in the first branch).

lib Foo
  fun foo =
    "bar"(Int32) : Int32
end

This example continues to raise a compiler error.

[ftarulla]

This should also apply to cases where the function name is a string literal (which is handled in the first branch).

lib Foo
  fun foo =
    "bar"(Int32) : Int32
end

This example continues to raise a compiler error.

Good catch! Thx @straight-shoota! I'll check it asap 🤓 👍

[beta-ziliani]

🚀