Fix multiple caches hash collision

What does this MR do and why?

When using multiple caches for a single project, it may lead to a cache collision due to how we are calculating the key. There is currently a workaround by using the prefix keyword, but we would like to fix this issue so that no workaround is necessary. This will only add a prefix if no prefix is specified.

Screenshots or screen recordings

Before	After

With cache:key:prefix, it does not add an index:

How to set up and validate locally

• Create a .gitlab-ci.yaml that has multiple cache keys that depend on the lock file.
• Run the pipeline
• See cache key collision:

Creating cache 25b4b97e42e1c8264602627bd9591c7428c46135-1-non_protected...
node_modules/: found 844 matching files and directories 

Creating cache 25b4b97e42e1c8264602627bd9591c7428c46135-1-non_protected...
folder2/node_modules/: found 2946 matching files and directories 

Example Project

• Example Project: https://gitlab.com/gitlab-gold/faleksic-tests/public-group/ci-testing/-/tree/cache-collision
• Example Pipeline: https://gitlab.com/gitlab-gold/faleksic-tests/public-group/ci-testing/-/jobs/2461580650

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.

Related: #362492 (closed)