Using an `include:` should be able to use project id instead of project path

Problem to solve

If the project path for the include files changes, this will cause all include statements to fail.
But if we used project id's instead of paths, then moving the project won't affect this at all.

Intended users

• Everyone who uses CI/CD

Further details

Biggest use case is when the template project is moved/renamed.
It shouldn't happen often, but may happen and its effects could be widespread.

Proposal

Allow the include path to be based on project id instead.
For example...

include:  
  - project: 'project:project-ID'  
    file: '/templates/.gitlab-ci-template.yml'

Links / references

The customer who is asking for this (internal link): https://gitlab.my.salesforce.com/0016100000W44Pc