Revert: Avoid looping over all type cache entries in TypeCacheRelCallback()
This commit reverts
c14d4acb8 as the patch design didn't take into account
that TypeCacheEntry could be invalidated during the lookup_type_cache() call.
Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/
1927cba4-177e-5c23-cbcc-
d444a850304f%40gmail.com