feat: add role var prefix option

[stopendy]

New Feature: role_var_prefix Option

This PR adds a new configuration option called role_var_prefix.

It allows us to tweak role variable's prefix pattern with regular expression. Common use cases include prefix role variable with collection name.

The default value is "^_*{role}_", which should be fully compatible with the previous implementation, where we should always prefix role variables with role name with further prefixing with underscore (_) being allowed.

If someone could review the concept and implementation and allow this PR to be merged, that would be great.

(Background) Existing Issues

This feature addresses following issues:

• rules var-naming[no-role-prefix] and var-naming[pattern] collide if var_naming_pattern is changed from default #4142
• var-naming[no-role-prefix] rule should accept collection roles vendor prefix #3909

It also covers following Ansible Forum discussions:

• Ansible-lint and the “role_” prefix on variable names in collections
• Role var/param naming (prefix)

[stopendy]

Hmm I guess auto-labeling CI failed because two labels were mixed up (feat/chore)? If that is the case I will have to fix up two commits into a feat commit.

Since I’m not familiar with CI, could someone confirm that my approach is worth trying? I don’t even know I can force push back and forth for testing here.

Or maybe maintainers could label this PR manually as feat instead.