Prevent reading & neon-decoding multiple times

[staabm]

before this PR:

➜  phpstan-src git:(2.1.x) ✗ hyperfine 'bin/phpstan analyze foob.php' -i
Benchmark 1: bin/phpstan analyze foob.php
  Time (mean ± σ):      1.114 s ±  0.009 s    [User: 0.752 s, System: 0.267 s]
  Range (min … max):    1.105 s …  1.128 s    10 runs
 
  Warning: Ignoring non-zero exit code.

after this PR:

➜  phpstan-src git:(neon-cache) ✗ hyperfine 'bin/phpstan analyze foob.php' -i
Benchmark 1: bin/phpstan analyze foob.php
  Time (mean ± σ):     992.7 ms ±  61.0 ms    [User: 679.0 ms, System: 265.5 ms]
  Range (min … max):   938.9 ms … 1077.7 ms    10 runs
 
  Warning: Ignoring non-zero exit code.

similar to #4645

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before this PR we read&decoded 46 NEON files in the above example.
after this PR we only need 28.

[ondrejmirtes]

Thank you!