Minimize slot creation for multi-inserts of pg_shdepend

Use multi-inserts for pg_attribute and pg_shdepend

Refactor ObjectAddress field assignments in more places

Refactor creation of normal dependency records when creating extension

Handle logical decoding in multi-insert for catalog tuples

Allow buffer tuple table slots to materialize after ExecStoreVirtualTuple().

Initialize variable to silence compiler warning.

Fix heap_getattr() handling of fast defaults.