Revert "Workaround for case 539074"

This reverts commit c293b1a314772eb232ec529497c1e632741d669f.
More localized workaround for case 539074.
Doesn't break stack traces in general,
and fixes the reported behavior.
We may be missing some other corner cases,
but we'll have to handle those as we come to them.
Fix MonoImage refcount leak that causes images to not be released on
domain unload which causes new domains to reuse old assemblies referenced
by a leaky image, causing all kinds of funky behaviour. Callers should
call mono_image_close after calling mono_assembly_load* to ensure things
don't leak.
Update STV sdk
Merge branch 'unity-staging' into stv