Support PHP 8.4; Add option --scss-deprecations for behat

[marinaglancy]

1. E_STRICT does not have any meaning since PHP 8.0 and is officially deprecated in PHP 8.4 (Addresses Errors when running on PHP 8.4 #344)
2. Add tests of moodle-plugin-ci on PHP 8.4
3. Add option --scss-deprecations for behat (Addresses Add an option to run behat tests with --scss-deprecations #343)
4. Bump PHP and postgres versions in Travis (not related to these issues but it was already failing)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.31%. Comparing base (f31fea1) to head (73bb7d7).
Report is 5 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main     #346      +/-   ##
============================================
+ Coverage     88.26%   88.31%   +0.04%     
- Complexity      761      762       +1     
============================================
  Files            77       77              
  Lines          2335     2344       +9     
============================================
+ Hits           2061     2070       +9     
  Misses          274      274              

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[marinaglancy]

lol I can't win with travis
Ubuntu focal (20.04) does not have PHP 8.4, Ubuntu jammy (22.04) does not have PHP 7.4

[marinaglancy]

Note: I did not add 8.4 to travis. Feel free to create a separate issue. It is outside of the scope of the problems I was solving and also outside of my knowledge and I do not have time to find the solution at the moment.