Add debug asserts

[jwood803]

Potential fix for #828

@briancylui Is this on the right track to what was needed? Do you think we should do the same to the AvxIntrinsics class, as well?

[TomFinley]

Hi @jwood803 , this approach looks good to me. Thank you for working on it. I'm not certain if @briancylui is still looking at this (he's quite welcome to, just don't think he is). You mention this is a WIP so I imagine there may be more to come, so I will not formally approve just yet.

For those methods that take AlignedArray, we might consider that also having a Contracts.AssertValue on the inputs would also be valuable (aligned array is a reference type), but I do not view this as in any way essential or required given that the ultimate goal would be (this pursuant to #1028 and likely followup work).

[Zruty0]

[Anipik]

@Zruty0 @danmosemsft can we revert this change ? some of the debug assumptions are not true. eg in matrix multplivation destionation and src length need not be same
And Currently Contracts.Assert() are being removed from netcoreapp3.0 build.

[jwood803]

@Anipik @Zruty0 I can make additional PRs for this. One to update the asserts and another to move away from Contracts.Assert.

[Anipik]

@jwood803 if you want to correct the change, just remove the contracts.Assert statements from the matMul, matMulTrans and matmulP in a PR ?