Fixes 1156 (Issue with scalar literals in code coverage)

[DeveloperRob]

This fixes #1156 by updating ExecutableLinesFindingVisitor.php so that where an expression is solely a string literal, float literal, integer literal (PHPParser\Node\Scalar) or null / true / false (PHPParser\Node\Expr\ConstFetch); the node is ignored / not marked as executable.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.32%. Comparing base (c5431e1) to head (195df3c).
⚠️ Report is 1 commits behind head on main.
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1157      +/-   ##
============================================
+ Coverage     82.31%   82.32%   +0.01%     
- Complexity     1562     1565       +3     
============================================
  Files           114      114              
  Lines          5315     5319       +4     
============================================
+ Hits           4375     4379       +4     
  Misses          940      940              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[sebastianbergmann]

Thank you for your contribution. I appreciate the time you invested in preparing this pull request. However, I have decided not to merge it as I think 3203ed6 is a "cleaner" solution.