GitLab

* Add wrapper 'generate-test-matrix' to be called without special arguments

* Rename "generate matrix" to "generate cheatsheet"
since that what's we call it. Also, create a direct script to run
everything with the correct options.

* Add missing file

* Document how to manage the cheatsheet

* Move unused patterns found in POLYGLOT to POLYGLOT/unused

* Add cheatsheet for bash

* Try to suppress semgrep warning

* Suppress semgrep warning, second try

* Change indentation to 2 spaces instead of 4 in cheatsheet.json,
so as to match expected style in semgrep-app.

* Update changelog

* Rename terraform -> hcl so as to fix cheatsheet exported to semgrep-app

* Move back POLYGLOT/unused/*.sgrep to POLYGLOT/ because these files are
used in the tests (but not in the cheatsheet)