Add wildcard support to cache + recursion detection

What does this MR do and why?

This MR has two commits:

1. Restore wildcard support in cache keys which broke with MR !203233 (merged). Additionally, this fixes a pre-existing bug in the search_files_by_wildcard_path where **/*.yml patterns failed to match root-level files. This commit is from the MR that had already been reviewed and is the one that got reverted.
2. Fixes a bug uncovered by another bug that was uncovered by a feature. The wildcard cache fix above made **/*.yml patterns work correctly, but this exposed a bug where a file could accidentally include itself via wildcard. This commit adds additional specs to protect against the bug that caused it.

Screenshots or screen recordings

Commit 2 - Example reproduction (from Slack thread):

#.gitlab-ci.yml
include:
  includes/all.yml

# icludes/all.yml
include:
  - 'includes/**/*.yml'

# includes/d1/job1.yml
job_1:
    script: env

# includes/d2/job2.yml
job_2:
    script: env

Commit 1 - original implementation, still testable this way:

To test different wildcard expansions, you can use the following config:

  test-cache:
    script:
      - echo "Testing cache keys"
    cache:
      - key:
          files: ['*.yml']
          prefix: 'single-wildcard'
        paths: ['vendor/']

      - key:
          files: ['**/*.yml']
          prefix: 'double-wildcard'
        paths: ['vendor/']

      - key:
          files: ['config.yml', '*.json']
          prefix: 'mixed-patterns'
        paths: ['vendor/']

The directory structure you should have is:

  my-project/
  ├── .gitlab-ci.yml         
  ├── config.yml             
  ├── package.json           
  ├── data.json              
  ├── config/
  │   ├── database.yml       
  │   └── settings.json       
  ├── deploy/
  │   └── production.yml      
  └── vendor/                 

Run a pipeline. In the logs, you should see the hash being appended to the caches:

Creating cache double-wildcard-<HASH>...

Without the fix, on master, this would be:

wildcard-default-23-protected

NO HASH

References

#572701 (closed)

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