Add "paths" to rules:changes

What does this MR do and why?

This is the third step of improving the rules:changes CI config. This will add an alias syntax for "rules:changes": "rules:changes:paths"

Related to #293645 (closed)

In the next step, compare will be added to rules:changes with paths.

Step	Status
1. Move CI rules-changes to an entry class	!89463 (merged)
2. Refactor CI rules entry to use composed value	!90238 (merged)
3. Add rules:changes:paths alias to rules:changes	👈 You are here
4. Implement rules:changes:compare	!90968 (merged)

Screenshots or screen recordings

These two syntaxes are the same:

test1:
  script: exit 0
  rules:
    - changes:
      - README.md

test2:
  script: exit 0
  rules:
    - changes:
        paths:
          - README.md

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.