Doing so will cause linkage errors and is not neccessary since we call
the witness of the enclosing type as soon as its fields are not ABI
accessible.
rdar://40868358
They're not used inside the thunk so it's a waste passing them in, and
if they involve private types from a different translation unit we will
get a linking error from referencing the metadata accessor function.
Fixes the test case in <rdar://problem/39470607>, but the more general
problem remains.
Fixes a regression in the source compatibility suite which I had a
lot of trouble extracting into a separate test case.
Most of this patch is just moving the outlining code into a separate
file and organizing it into a helper class instead of copy/pasting
so much code. The main functional change is implicit in the difference
between collecting formal metadata and collecting it for layout, which
then is exploited in bindMetadataParameters.
As a secondary change, stop collecting metadata for class-bounded
archetypes; we don't actually need it to do value operations.
