Reduce the Capacity of the Handler List Creation

[JasonBock]

Describe the solution you'd like

Whenever I create a handler list, I use the default size (which is 4 as of .NET 8....I think it's been that way for a while):

private readonly global::System.Collections.Generic.List<global::Rocks.Handler> @handlers0 = new();

I think the typical usage of a mock is to only set one or two expectations. So, maybe the correct thing to do is to set them all to 2:

private readonly global::System.Collections.Generic.List<global::Rocks.Handler> @handlers0 = new(2);

Maybe even setting it to 1 would be ideal. Not sure. Maybe having an optional parameter for the expectation creation would allow users to set the capacity size, but....I'm not sure that's worth it.

[JasonBock]

I just realized that if you don't provide a capacity, then the array is set to one that has zero capacity. So....I'm not sure if my idea will help - it may actually hurt, though....it might help because, again, I'm betting that most mock usage will only set one or two expectations, so changing the default capacity size could help on a resize.

[JasonBock]

Actually, setting the initial capacity to a value like 2 isn't what I want, because that would actually allocated an array of length 2. What I might do is set all of the lists as a nullable type, like this:

private readonly global::System.Collections.Generic.List<global::Rocks.Handler>; @handlers0;

When an expectation is set, I'd make a check to create the list if it's not created (this won't be thread-safe):

if (this.Expectations.handlers0 is null ) { this.Expectations.handlers0 = new(); }
this.Expectations.handlers0.Add(handler);
return new(handler);

This would mean we'd have to do null checks when we look at the .Count values:

if (this.Expectations.handlers0?.Count > 0)

We also need to check for this in .Verify(). I should do this together with #292