Stop RCS1031, RCS1208 and RCS1211 from being applied if the local variables overlap.

[jamesHargreaves12]

For cases, where the same local variable is declared inside the if and else blocks e.g.

if (flag)
{
    var x  = 1;
    return x;
}
else 
{
    var x = 0;
    return x;
}

The diagnostic RCS1211 Should not be raised.

Removing the else block would cause a compiler error "A local variable named 'x' cannot be declared in this scope because it would give a different meaning to 'x', which is already used in a parent or current scope to denote something else".

The same thing is true for switch case brackets (RCS1031).

[josefpihrt]

Thanks for the PR! 👍