findStartOfStatement doesn't work correctly inside switch

[VincentLanglet]

Code sample

switch ($foo) {
    case 1:
        return 2;
    case 2:
        return 4;
}

Describe the bug
When working on #3186, I got a weird behavior with the scope opener/closer of switch/case. In the code sample, when I dump the tokens, : is the scope opener of the scope_condition case, and return is the scope closer.

Seems like it's because of this: https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Tokenizers/PHP.php#L220

But then, when using the findStartOfStatement with the index of the token 4, it will return the token 4 instead of the return one, because of this condition: https://github.com/squizlabs/PHP_CodeSniffer/blob/master/src/Files/File.php#L2311-L2319
Return is a scope closer here so it return the value before return (or after, since we're looking backward), which is 4.

So I think we should ignore the scope closer of the switch/case, the right fix would be this: e790378