[12.x] Ensure mailable HTML assertions properly escape quotes

[jackbayliss]

Closes #58586

When using assertSeeInHtml() escape is true by default but, apostrophes and quotes are not being properly escaped, causing assertions to fail such as:

// Blade template: {{ "It's a wonderful day" }}
// Renders as: It's a wonderful day in HTML

$mailable->assertSeeInHtml("It's a wonderful day"); // Would fail...

The fix ensures that quotes are properly escaped to match Blade's HTML escaping.. withQuote was being set based on if the markdown property was set, where as I think it should be left as true.. (its true by default) - to match the escape default.

I've targeted 12.x as everything passes and this only alters the assertion behaviour I can't think of a scenario where you'd expect it to not escape quotes etc, can target 13.x if you prefer! but felt like an oversight perhaps.

Have added a test to prevent regression 🫡

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[taylorotwell]

Hmm, so why the previous code there in the first place? When was it added and why?

[jackbayliss]

@taylorotwell

It was added as part of #54737 but the tests added in that PR still pass with this change.

This exact same issue was fixed 3 years ago here #42923, but I believe it was re introduced with the above.

Perhaps @crynobone can answer that better?

🫡

[crynobone]

The previous PR focus on Markdown usage and missed out example from just base view.

[jackbayliss]

Thanks @crynobone !