Reduce enumerations and delegate invocations

[paulomorgado]

Replace the internal allocations of the used LINQ operators by a hashtable of assembly names.

Note: the existing code used Enumerable.Count() when Enumerable.Any() could be used.

[Tratcher]

Thanks for the interest, but I don't think we need to work on this code path. The plan is to obsolete this component (#20964). It also only runs at startup so minor allocations aren't a concern.

[davidfowl]

We care now about rescuing startup time (as part of the inner loop improvements) so this is now fair game.

[Tratcher]

Note: the existing code used Enumerable.Count() when Enumerable.Any() could be used.

Not quite. Any means > 0, but the check in this code is > 1.

[Tratcher]

Approving because this is small and already done, but see our other conversation about focusing on more critical code paths.

[davidfowl]

@Tratcher is right, this change is fine but we're going to be obsoleting this type so avoid making further changes here.