Add --yang-no-newlines option

[telia-ok]

• Add output YANG option to not insert newlines after __force_newlinearg

pyang --help:

    --yang-no-newlines  Don't insert newlines after ('description',
                        'reference', 'contact', 'organization')

[fredgan]

why you need this feature? What are the usage scenarios？

[telia-ok]

When we work on large YANG models this change can reduce the total number of lines by several hundred when formatting the YANG file with pyang.

A lot of our descriptions have short descriptions so there's no need to split them up into two lines. Example:

    `description "VSI  ID";`

vs.

description
          "VSI  ID";

Easier to read and keeps the total number of lines down. This is an optional flag and won't affect the default behavior.