sql: add regression tests for memory accounting bug

Add regression tests for a bug where backfilling a computed column or a column
with a default value using a builtin function would cause a `memory budget
exceeded` error (cockroachdb#34901). This was fixed by cockroachdb#34935.

Release note: None

pkg/sql/logictest/testdata/logic_test/computed

@@ -746,3 +746,19 @@ CREATE TABLE x (
 
 query error value type decimal doesn't match type INT8 of column "a"
 INSERT INTO x VALUES(1.4)
+
+# Regression test for #34901: verify that builtins can be used in computed
+# column expressions without a "memory budget exceeded" error while backfilling
+statement ok
+CREATE TABLE builtin_table (x STRING)
+
+statement ok
+INSERT INTO builtin_table VALUES ('a')
+
+statement ok
+ALTER TABLE builtin_table ADD COLUMN y STRING AS (concat(x, 'b')) STORED
+
+query TT
+SELECT * FROM builtin_table
+----
+a  ab

pkg/sql/logictest/testdata/logic_test/default

@@ -117,3 +117,19 @@ column_name  data_type  is_nullable  column_default  generation_expression  indi
 a            INT8       false        NULL            ·                      {primary}  false
 b            TIMESTAMP  true         NULL            ·                      {}         false
 c            INT8       true         NULL            ·                      {}         false
+
+# Regression test for #34901: verify that builtins can be used in default value
+# expressions without a "memory budget exceeded" error while backfilling
+statement ok
+CREATE TABLE builtin_table (x STRING)
+
+statement ok
+INSERT INTO builtin_table VALUES ('a')
+
+statement ok
+ALTER TABLE builtin_table ADD COLUMN y STRING DEFAULT (concat('b', 'c'))
+
+query TT
+SELECT * FROM builtin_table
+----
+a  bc