Structural Equality: Treat ImmutableArray<T> the same as Array

[NightOwl888]

Since ImmutableArray<T> is yet another array implementation of IStructuralEquatable that could be compared against Array, it must be treated like an Array, not compared using IStructuralEquatable.

There are several places in the codebase where we do this:

• CollectionUtil
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/ArrayEqualityUtil.cs#L114
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/ArrayEqualityUtil.cs#L259
• StructuralEqualityComparer
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/StructuralEqualityComparer.cs#L83
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/StructuralEqualityComparer.cs#L133
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/StructuralEqualityComparer.cs#L177
  • https://github.com/NightOwl888/J2N/blob/b7f80ca424af2b077b5d42beff4d9fbad8b05ef5/src/J2N/Collections/StructuralEqualityComparer.cs#L208

Unfortunately, we have some challenges to deal with, since if we don't know the generic closing type of ImmutableArray<T>, we will need to do some work to materialize it before we can compare it.