collections should be defined at the project root and not relative to playbooks path

[RusticPotatoes]

collections was being referenced from the playbooks relative directory and should be from the projects root directory. updated roles for consistency on path joining. thanks @andreas-marschke for the original find, updating the current codebase as there has been so many changes.

if a playbook is in <proj_root>/sub_folder/playbook.yml the previous code expects collections to be in the sub_folder directory <proj_root>/sub_folder/collections/requirements.yml.

my proposed changes sets the collections directory to always be in the projects root folder as it does for roles directory currently.

Now it will look for collections in <proj_root>/collections/requirements.yml as expected.

this resolves issue https://github.com/ansible-semaphore/semaphore/issues/1144 for No collections requirements file found