Perf: Reduce the number of convention executions

[AndriySvyryd]

• Validate ConventionSet doesn't have duplicate convention registrations
• When executing delayed conventions prune redundant ones
  • Latter invocations overriding former ones: PropertyRemoved after PropertyNullabilityChanged
  • Cancelling-out invocations: IndexAdded after IndexRemoved on the same properties
• Don't call conventions when resetting to default value that is the same as the current one
• Don't store delayed convention executions if no conventions are registered
• Store derived types to improve DerivedTypeDiscoveryConvention perf