Fixed implicit conversion from float to int in Mage_SalesRule_Model_Validator

[kyrena]

Description

This PR fix Implicit conversion from float 10.1 to int loses precision with PHP 8.1/8.2, with a coupon code of 10.1% for all items of cart.

See also this discussion comment.

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[fballiano]

Actually I'm not sure I get the reason behind this PR, why cast to 10 if the discount is 10.1? I understand that 10.1 is an unusual number but remove the possibility for decimal discounts doesn't seem the way to go, to me.

[fballiano]

So, I checked that part of the core, I think casting to string is much better, that variable is only used as an array_key, so as a string we risk less conflict if a cart as 2 discounts of the same value (at least for the integer part).

I think the core is wrong in this part, they shouldn't have used the discount percent as a key, but the rule id, or something unique.

[kiatng]

Is this PR fixing a bug?