Use pattern matching in the comparers #4065

Most of the comparers perform type-checking using the following pattern:

if (x is DesiredType)
  ((DesiredType)x).DoSomething()

Newer versions of C# added the ability to avoid the second cast by defining a temp variable.

if (x is DesiredType dt)
  dt.DoSomething()

This helps simplify code and provides a small perf boost by avoiding an unneccessary cast. This could also minimize future changes if the comparers ever get a generic overload as pattern matching can play nicer than casts in that case