Perf: Refactor PHPUnitVersionDetector to use runtime reflection

[staabm]

before this PR running

➜  phpstan-src git:(2.1.x) ✗ cat foob.php                                                                                             
<?php

function doFoo(A $a)
{

}

➜  phpstan-src git:(2.1.x) ✗ bin/phpstan analyze foob.php --xdebug --debug

 ! [NOTE] You are running with "--xdebug" enabled, and the Xdebug PHP extension is active.                              
 !        The process will halt at breakpoints, but PHPStan will run much slower.                                       
 !        Use this only if you are debugging PHPStan itself or your custom extensions.                                  

Note: Using configuration file /Users/staabm/workspace/phpstan-src/phpstan.neon.dist.
/Users/staabm/workspace/phpstan-src/foob.php
 ------ ------------------------------------------------------ 
  Line   foob.php                                              
 ------ ------------------------------------------------------ 
  3      Function doFoo() has no return type specified.        
         🪪  missingType.return                                
         at foob.php:3                                         
  3      Parameter $a of function doFoo() has invalid type A.  
         🪪  class.notFound                                    
         at foob.php:3                                         
 ------ ------------------------------------------------------ 


                                                                                                                        
 [ERROR] Found 2 errors                                                                                                                                                                                                                    

would invoke FileReader::readFile() 188 times.

after this PR it is only invoked 62 times.

-> we reduce bootstrap overhead when projects have phpstan-phpunit installed
-> similar idea as in phpstan/phpstan-src#4491, refs phpstan/build-infection#16

---

using phpstan/phpstan-src@38ea1ab

before this PR:

➜  phpstan-src git:(2.1.x) ✗ hyperfine 'bin/phpstan analyze foob.php --debug' -i
Benchmark 1: bin/phpstan analyze foob.php --debug
  Time (mean ± σ):     749.7 ms ±   6.1 ms    [User: 577.5 ms, System: 167.0 ms]
  Range (min … max):   745.0 ms … 762.4 ms    10 runs
 
  Warning: Ignoring non-zero exit code.

after this PR:

➜  phpstan-src git:(2.1.x) ✗ hyperfine 'bin/phpstan analyze foob.php --debug' -i
Benchmark 1: bin/phpstan analyze foob.php --debug
  Time (mean ± σ):     726.2 ms ±  16.3 ms    [User: 550.9 ms, System: 169.2 ms]
  Range (min … max):   715.0 ms … 769.7 ms    10 runs
 
  Warning: Ignoring non-zero exit code.

[staabm]

do we really need this is_file or could we just drop it, because we already do @file_get_contents($phpUnitComposer); which would swallow the error nevertheless?

[ondrejmirtes]

Could be dropped :)

[staabm]

here we go.

[ondrejmirtes]

Could be dropped :)

[ondrejmirtes]

Thank you!