Don't remove existing uses if they are the same as the created string for use statements

[junichi11]

• [PHP] Multiple default namespace navigator fix, FixImports for the whole file #5681
• Avoid changing the file state if the created string is the same as the existing use statements

[junichi11]

I've fixed #5681 again.
I didn't fix the "multiple default namespaces" issue because I didn't think it's important.
I don't think many people use the following case.

<?php
namespace {
    class DefaultA {}
}

namespace MyNamespace {
    class MyClass {}
}

namespace {
    class DefaultB {}
}

I'm not sure the reason why a user would like to separate it.
Usually, it should be used the following, I think.

<?php
namespace {
    class DefaultA {}
    class DefaultB {}
}

namespace MyNamespace {
    class MyClass {}
}

I hope that the regressions are resolved in NB19.

[tmysik]

@junichi11 I agree, it makes sense to me. We can always wait for a new report.