Fix #78308: IntlPartsIterator key is wrong for KEY_LEFT/KEY_RIGHT

[cmb69]

We must not increase the iterator's index after it has been properly
determined. A clean solution would be to increment the index in the
internal *_move_forward() methods instead of IntlIterator::next(),
but since the *_move_forward() methods are currently also called by
the internal *_rewind() methods, and don't have a flag to determine
the (intent of the) caller, we apply a hack for now.

We also fix the erroneous expectations of an existing test case.

[nikic]

A clean solution would be to increment the index in the
internal *_move_forward() methods instead of IntlIterator::next(),
but since the *_move_forward() methods are currently also called by
the internal *_rewind() methods, and don't have a flag to determine
the (intent of the) caller, we apply a hack for now.

As these are static functions we are free to change them -- maybe directly go with the "clean" solution?

[cmb69]

I'm uneasy to do this as bugfix targeting PHP-7.2.

[cmb69]

@smalyshev, what do you think?

[TRowbotham]

Hi @cmb69, since I reported this bug I just wanted to followup given that 7.2's active support ends in 10 days and this fix seems to be stalled on a question about including it in 7.2.

[cmb69]

I don't think that we should fix it for 7.2 any longer. I'm neither comfortable merging the hack presented by this PR, nor by merging a clean solution into the last bugfix release.

[cmb69]

I'm going to close this PR. It probably makes no sense to have this hackish solution in PHP 7.4, and I hope someone comes up with a clean solution for PHP 8.x.