Emphasised IEqualityComparer members are a pair

A correct impl of IEqualityComparer needs to implement all members in a
semantically correct manner
Replaced unsafe IEqualityComparer GetHashCode

GetHashCode must not incorrectly bucket objects for a consumer of
IEqualityComparer [`1] to be able to rely on the result of Equals solely
on objects bearing the same hash code being authoritative
Added new RandomRangedGenerator test using PLINQ for thread safety testing.
Removed original slower RandomRangedGenerator async test
Changed test  to use Assert.DoesNotThrow instead of try-catch
Parameterized test, changed name back to original name.  Changed assert back to try-catch.
Removed try-catch from test so AggregateException will now bubble up to test runner.
Merge branch '227-randomrangedgeneratortest-performance' of https://github.com/dlongest/AutoFixture into dlongest-227-randomrangedgeneratortest-performance