[3.x] Support pages with more output file extensions (Fix conflicting states)

[emmadesilva]

Fix Broken Static/Instance Symmetry in InMemoryPage

We introduced $exactOutputPath as an instance-level boolean flag on InMemoryPage, but HydePage path resolution relies heavily on static methods.

Because exactOutputPath is stateful, InMemoryPage now has a dangerous inconsistency: instance methods return the exact output path, while static methods still assume HTML output.

$page = InMemoryPage::file('robots.txt', ...);

// The instance method works correctly:
$page->getOutputPath(); // "robots.txt"

// The static method incorrectly applies the HTML fallback:
InMemoryPage::outputPath('robots.txt'); // "robots.txt.html"

Fixes an unreleased issue introduced in #2524

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (0e7f2b2) to head (d9b070e).
⚠️ Report is 8 commits behind head on v3/non-html-pages.

Additional details and impacted files

@@                  Coverage Diff                  @@
##             v3/non-html-pages     #2541   +/-   ##
=====================================================
  Coverage               100.00%   100.00%           
+ Complexity                1793      1782   -11     
=====================================================
  Files                      179       179           
  Lines                     4472      4453   -19     
=====================================================
- Hits                      4472      4453   -19     

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