pam_limits setting has several issues

[widhalmt]

In role elasticsearch we set limits for Elasticsearch. This should be done by the Elasticsearch package, but didn't work in the past. I have to confess, I didn't track if works with current versions.

So this issue covers several parts:

• Changing pam_limits might not be desirable for every setup. We should allow for deactivating this task. The default depends on the following items
• Maybe it's not neccessary anymore. If not, we can either remove the task completely or leave it but set the default to false
• If it's still needed (At least in some setups) we should keep it and add a variable to deactivate it if you really don't want it
• The module pam_limits is part of the community.general collection which is not available in every kind of installation of Ansible. We need to add it to requirements. In Readme as well as in our Molecule tests.