Use the correct PG_DETOAST_DATUM macro in BRIN

Commit 6bcda4a replaced PG_DETOAST_DATUM with PG_DETOAST_DATUM_PACKED
in two BRIN output functions, for minmax-multi and bloom opclasses. But
this is incorrect - the code is accessing the data through structs that
already include a 4B header, so the detoast needs to match that. But the
PACKED macro may keep the 1B header, which means the struct fields will
point to incorrect data.

Backpatch-through: 16
Discussion: https://postgr.es/m/1df00a66-db5a-4e66-809a-99b386a06d86%40enterprisedb.com

Author: tvondra

src/backend/access/brin/brin_bloom.c

@@ -800,7 +800,7 @@ brin_bloom_summary_out(PG_FUNCTION_ARGS)
 	StringInfoData str;
 
 	/* detoast the data to get value with a full 4B header */
-	filter = (BloomFilter *) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(0));
+	filter = (BloomFilter *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
 
 	initStringInfo(&str);
 	appendStringInfoChar(&str, '{');

src/backend/access/brin/brin_minmax_multi.c

@@ -3023,7 +3023,7 @@ brin_minmax_multi_summary_out(PG_FUNCTION_ARGS)
 	 * Detoast to get value with full 4B header (can't be stored in a toast
 	 * table, but can use 1B header).
 	 */
-	ranges = (SerializedRanges *) PG_DETOAST_DATUM_PACKED(PG_GETARG_DATUM(0));
+	ranges = (SerializedRanges *) PG_DETOAST_DATUM(PG_GETARG_DATUM(0));
 
 	/* lookup output func for the type */
 	getTypeOutputInfo(ranges->typid, &outfunc, &isvarlena);