Do not assert RyuJIT if InitializeArray cannot be expanded (#86373)

Do not assert RyuJIT if InitializeArray cannot be expanded (#86373)

Found in Pri0 tests. `RuntimeHelper.InitializeArray(default, default)` would assert RyuJIT. Do not assert.

The tests also have various invalid combinations of the intrinsic that make it difficult to do optimized builds (we don't want the target field to become reflectable in the common cases but also failing to predict when this doesn't expand results in scanning failures due to unmet reflection dependencies).

Give up on trying to predict when intrinsic expansion kicks in and instead lean into RVA statics not being expressible in C# and the fields not being reflection-invokable anyway.