[Swift5] Add useClasses cli option

[aymanbagabas]

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[4brunu]

Looks good to me 👍
CI is failing, but it's not related to this PR.

[wing328]

@aymanbagabas thanks for the PR. Are there supposed to be changes to the mustache templates as well?

[aymanbagabas]

@wing328 The template changes are already there from 0f5e7d1 #9205

[wing328]

👌