BUG: fix item cache invalidation bug in #3970 caused by is_mixed_type silently consolidating (hurf). also fix stable sorting bug presenting on my machine
Merge branch 'fix-consolidate-cache-invalidation-gh3970' of https://github.com/wesm/pandas into wesm-fix-consolidate-cache-invalidation-gh3970
CLN: have _consolidate_inplace invalidate the cache when needed