Implement better diff for run-tests.php

[iluuu1994]

Diffing algorithm is borrowed from sebastian/diff

Fixes GH-10806

@mvorisek Does this fix the problem for you?

[nielsdos]

Nit: I think it would be a bit nicer if the diffing code of bless_tests.php and the now run-tests.php was extracted to a separate .php file that can be included, to reduce duplication. :)

[iluuu1994]

The file is part of the distribution and might be copied separately, I wanted to avoid a new file that has to be copied for it to stay functional. Maybe we could create a functional diff file though that can be patched to avoid the diffing in bless.php.

[nielsdos]

Aha okay, TIL. Best to ignore my comment then :-)

[mvorisek]

Thank you. I can confirm this PR fixes the issue described in #10806.

to reduce duplication

I wanted to avoid a new file that has to be copied for it to stay functional.

AFAK this is required for run-tests.php, bless_tests.php is internal file only, what about including run-tests.php from bless_tests.php and dedupling bless_tests.php instead?

[iluuu1994]

Turns out that algorithm uses a lot of memory (~200MB for a failing ASAN test, which is why the ASAN build crashed). I've switched it out for sebastian/diff with the MemoryEfficientLongestCommonSubsequenceCalculator. It still needs to be cleaned up, so no need for a review just yet.

[iluuu1994]

This should be ready. Since it's using a different algorithm from bless_tests.php uniforming them is no longer relevant, or can be done in a separate step.

[iluuu1994]

@mvorisek Sorry, since I basically completely changed the implementation it would be great if you could retest if this solves the problem for you.