Ensure extracting candidates from JS embedded in a PHP string works as expected

[RobinMalfait]

This PR fixes an issue where candidates are not properly extractor when they end in \. This can happen if you embed a programming language like JS inside another language like PHP where you need to escape some strings.

Here is an example of Livewire flux:

@php
if ($sidebarIsStashable) {
    $attributes = $attributes->merge([
        'x-init' => '$el.classList.add(\'-translate-x-full\'); $el.classList.add(\'transition-transform\')',
        //                                                ^                                            ^
    ]);
}
@endphp

<div x-data {{ $attributes->class('border-r w-64 p-4 min-h-dvh max-h-dvh top-0 fixed left-0') }}>
    {{ $slot }}
</div>

Where the \' is causing some issues.

Another solution might be to add a custom pre processor for blade files where we drop the escaped characters, but that felt overkill for now because some escapes are still valid.

Fixes: #17023

Test plan

1. Added a test to cover this case.
2. Existing tests still pass