CLI-1413: Set PHP compatibility level

[danepowell]

Motivation

Fixes CLI-1413

Proposed changes

Set compatibility level according to acquia/coding-standards-php#37

Alternatives considered

Testing steps

1. Follow the contribution guide to set up your development environment or download a pre-built acli.phar for this PR.
2. Clear the kernel cache to pick up new and changed commands: ./bin/acli ckc
3. (add specific steps for this pr)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.78%. Comparing base (cef7a69) to head (57b3086).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #1807   +/-   ##
=========================================
  Coverage     92.78%   92.78%           
  Complexity     1818     1818           
=========================================
  Files           122      122           
  Lines          6817     6817           
=========================================
  Hits           6325     6325           
  Misses          492      492           

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[github-actions]

Try the dev build for this PR: https://acquia-cli.s3.amazonaws.com/build/pr/1807/acli.phar

curl -OL https://acquia-cli.s3.amazonaws.com/build/pr/1807/acli.phar
chmod +x acli.phar