Upgrade to PHPUnit 9, drop PHP 7.2 support

[osma]

Reasons for creating this PR

We want to upgrade to PHPUnit 9 in order to stay up to date. It requires at minimum PHP 7.3, so this PR will also drop support for PHP 7.2.

Link to relevant issue(s), if any

• Closes Drop support for PHP 7.2, upgrade to PHPUnit 9 #1291

Description of the changes in this PR

• upgrade to PHPUnit 9.5.* (from 8.5.*) in composer.json and in GitHub Actions CI workflow
• migrate phpunit.xml configuration file using PHPUnit built in migration tool
• avoid using the deprecated expectException with PHP Errors, use expectError instead
• fix an invalid coverage annotation that wasn't previously noticed
• disable running GitHub Actions CI tests under PHP 7.2
• remove the rules that prevented collecting code coverage on PHP 8.0 (it didn't work under PHPUnit 8 but now works)

Known problems or uncertainties in this PR

none so far 🤞

Checklist

• phpUnit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works (if not, explain why below)
• The PR doesn't introduce unintended code changes (e.g. empty lines or useless reindentation)

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!   

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

No Coverage information
0.0% Duplication

[codecov]

Codecov Report

Merging #1312 (50965a4) into master (863b7cb) will increase coverage by 0.92%.
The diff coverage is n/a.

@@             Coverage Diff              @@
##             master    #1312      +/-   ##
============================================
+ Coverage     69.44%   70.36%   +0.92%     
+ Complexity     1656     1649       -7     
============================================
  Files            32       32              
  Lines          4068     3790     -278     
============================================
- Hits           2825     2667     -158     
+ Misses         1243     1123     -120     

Impacted Files	Coverage Δ
controller/Honeypot.php	40.90% <0.00%> (-7.10%)	⬇️
model/resolver/LOCResource.php	55.55% <0.00%> (-4.45%)	⬇️
model/sparql/JenaTextSparql.php	90.00% <0.00%> (-2.00%)	⬇️
model/resolver/WDQSResource.php	92.85% <0.00%> (-1.59%)	⬇️
model/sparql/GenericSparql.php	91.27% <0.00%> (-0.98%)	⬇️
model/PluginRegister.php	71.76% <0.00%> (-0.86%)	⬇️
model/VocabularyConfig.php	95.48% <0.00%> (-0.70%)	⬇️
model/ConceptMappingPropertyValue.php	82.82% <0.00%> (-0.51%)	⬇️
controller/RestController.php	22.38% <0.00%> (-0.38%)	⬇️
model/ConceptProperty.php	96.42% <0.00%> (ø)
... and 3 more

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[joelit]

Tested locally, works fine! :)