Move code quality report checking/concatenation into standalone script
Detailed Description
The CI has a .concatenate-code-quality template which checks code quality reports for any warnings (cf !2495 (merged)) and can also concatenate multiple reports from a single job.
This MR moves that template into a standalone script common/gitlab-ci-scripts/check_code_quality_reports, making it easier to read and edit.
Since the CI jobs that build from tarballs do not check out the Git repository, the .make-dist template now saves the common/gitlab-ci-scripts/ directory (formerly common/code-quality-scripts/) to the artifacts, alongside the tarballs, so that downstream jobs have access to the script.
API Changes
Please tick one of the following options:
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These changes do not modify the API. 
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These changes do modify the API, and are backwards compatible. 
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These changes do modify the API, and are backwards incompatible. 
For examples of changes that do not modify the API and/or are considered backwards (in)compatible, please see the contributing guide.