sql: add information_schema._pg_interval_type builtin

This commit adds an implementation for the
`information_schema._pg_interval_type` builtin.

The builtin is implemented as a user-defined function in Postgres
[here](https://github.com/postgres/postgres/blob/master/src/backend/catalog/information_schema.sql)

Needed for: #109603
Epic: none

Release note (sql change): The `information_schema._pg_interval_type`
builtin function is now supported, which improves compatibility with
PostgreSQL.

pkg/sql/logictest/testdata/logic_test/pg_builtins

@@ -974,3 +974,29 @@ select information_schema._pg_datetime_precision(1186, NULL);
 NULL
 
 subtest end
+
+subtest information_schema._pg_interval_type
+
+query T
+SELECT information_schema._pg_interval_type(1, 0);
+----
+NULL
+
+statement ok
+CREATE TYPE u AS (ufoo interval, ubar interval HOUR TO MINUTE);
+
+query TTT colnames
+SELECT a.attname,
+       t.typname,
+       information_schema._pg_interval_type(a.atttypid, a.atttypmod)
+FROM pg_attribute a
+JOIN pg_type t
+ON a.atttypid = t.oid
+WHERE a.attname IN ('ufoo', 'ubar')
+ORDER BY a.attname
+----
+attname  typname   information_schema._pg_interval_type
+ubar     interval  NULL
+ufoo     interval  NULL
+
+subtest end

pkg/sql/sem/builtins/fixed_oids.go

@@ -2509,6 +2509,7 @@ var builtinOidsArray = []string{
 	2538: `information_schema._pg_char_octet_length(typid: oid, typmod: int4) -> int`,
 	2539: `pg_encoding_max_length(encoding: int) -> int`,
 	2540: `information_schema._pg_datetime_precision(typid: oid, typmod: int4) -> int`,
+	2541: `information_schema._pg_interval_type(typid: oid, typmod: int4) -> string`,
 }
 
 var builtinOidsBySignature map[string]oid.Oid

pkg/sql/sem/builtins/pg_builtins.go

@@ -2275,6 +2275,26 @@ var pgBuiltins = map[string]builtinDefinition{
 		},
 	),
 
+	// https://github.com/postgres/postgres/blob/master/src/backend/catalog/information_schema.sql
+	"information_schema._pg_interval_type": makeBuiltin(tree.FunctionProperties{Category: builtinconstants.CategorySystemInfo},
+		tree.Overload{
+			Types: tree.ParamTypes{
+				{Name: "typid", Typ: types.Oid},
+				{Name: "typmod", Typ: types.Int4},
+			},
+			ReturnType: tree.FixedReturnType(types.String),
+			Body: `SELECT
+						 CASE WHEN $1 IN (1186) /* interval */
+			 								THEN pg_catalog.upper(substring(pg_catalog.format_type($1, $2), 'interval[()0-9]* #"%#"', '#')) 
+			        		ELSE null
+  			     END`,
+			Info:              notUsableInfo,
+			Volatility:        volatility.Immutable,
+			CalledOnNullInput: true,
+			Language:          tree.RoutineLangSQL,
+		},
+	),
+
 	"nameconcatoid": makeBuiltin(
 		tree.FunctionProperties{
 			Category: builtinconstants.CategorySystemInfo,