Deprecate `role_name` in `meta/main.yml`

During the Galaxy CLI Developer Workflow meeting we decided that Galaxy and Mazer should no longer synthesize the role (or repository) name, and therefore role_name needs to be deprecated.

For reference see: https://docs.google.com/document/d/1nx65quXCyYORNel72rRCovyQo_qO5fhHlqrnKyYNlYU/edit?usp=sharing

To let users know about this change, we need to start issuing a deprecation warning in the import output whenever role_name is found in meta/main.yml.

[oneswig]

A datapoint for your consideration:

As users of Galaxy our setup is broken by this proposal. The repos that back our Galaxy roles are in some cases widely used, forked and cloned. They all use the implicit naming convention of an ansible-role- prefix.

We have just been hit by having all our roles unexpectedly renamed to use underscores. What do you suggest users like us (and users of our roles) should do to maintain consistent developer and user experiences?

[brtknr]

Deprecating role_name is a terrible idea considering the fact that this is what people started doing to give their role the name they actually wanted rather than ansible_role_blah_blah… given than the regex to remove the ansible_role part was removed quite recently… this is going to be another costly blow and major annoyance to many users who have just reconfigured their pipelines.

Also, why did you remove the hyphens? Only noticed this change today and this seems like another, quite frankly, poorly justified change that adds little benefit.