Warn against allocating comparisons

[yaakov-h]

Similar but different to #177.

Things like switch (value.ToUpperInvariant()) { ... } or value.ToUpperInvariant() switch { ... }.

[brian-reichle]

What is the replacement? I don't think we can provide a comparer to a switch statement, so are you suggesting to replace the switch with a dictionary? That could be tricky from a CodeFix perspective.

[yaakov-h]

I'm not sure this one could have a code-fix. The best suggestion I have would be if-else-if-else-if- blocks, which depending on the circumstance might benefit from specific micro-optimizations anyway that we can't easily predict.