Task: Update HashSet<T> implementation to match .NET 8 behavior

[NightOwl888]

.NET 8 changes some collection behaviors. The test framework tests per interface and uses boolean switches to control tests for specific behaviors. We have configured the switches to make the tests pass based on the current behaviors rather than ensure they are in sync with .NET 8. So, the task is to go through the HashSet<T> implementation, bring in all changes between .NET 5 and .NET 8, and do the same with the HashSet<T> tests, setting each of the boolean switches to match .NET 8 (as appropriate).