Add sorting for snippet area / default snippets by title instead of key

[stollr]

Q	A
Bug fix?	no
New feature?	no
BC breaks?	in a way, but only very low break
Deprecations?	no
Fixed tickets	-
Related issues/PRs	-
License	MIT
Documentation PR	-

What's in this PR?

Changed the sorting of the snippet areas. They are sorted by title instead of their key (which is not visible in the frontend).

Why?

Currently the snippet areas are sorted by their key. But this makes it harder to scan the list for the user because titles may have the wrong order.

Note

I am using PHP's Collate class for comparing the string. But this is only available if the intl extension is loaded. So I have added a fallback to simple strcmp function, because the intl extension is not a requirement by Sulu.
But I am unsure how to handle this in the unit tests. Is it okay how it is done?

[alexander-schranz]

I like the idea. What I think we need to test here if the template uses translation-keys if that is correctly handled already.

As Sulu will always support 2 ways of define a title:

Have every meta inlined this way:

    <meta>
        <title lang="en">Example</title>
        <title lang="de">Beispiel</title>
    </meta>

or using a translation key:

    <meta>
        <title>app.example</title>
    </meta>

I think the second one sadly is not everywhere correctly target in the snippet area. See #7188. Maybe @mamazu can have a look if this would break his pull request or if we fine to go with it.

[mamazu]

Well, in the current version of Sulu using translations for the snippet areas is not supported. However if you merge my PR this PR would still work as the sorting happens in the controller and the translations are resolved in a compiler pass. So feel free to merge this.