update ansible module names to ansible collections names + remove of deleted ppa + inttention/lengthcheck correction

[TheRojam]

i updated ansible module names to ansible collections names which comes w/ ansible 2.9 atleast since ansible changed module to collections because the lack of name space and declutter.
Therefore i also updated the min_ansible_version to 2.9.
I also removed the stop to add the deleted ppa of wireguard since its now in the ubuntu repositories.
One commit is just a "typo" correction.
May lets improve this this w/ another pr at @botto repo.
Any remarks? lets discuss

[TheRojam]

after this i corrected a wrong intention in the publickeyfile and corrected the check for the empty variables to an check for zero length.
last point was mentioned as warning by ansible-lint.

[amotl]

Hi Anton,

thank you so much for giving some love to this module. We will be happy if you continue to bring more improvements to the code base, see also #2.

With kind regards,
Andreas.