test(contrib/drivers/gaussdb): add soft time, with, scanlist test coverage (#4686)

## Summary
- Port 3 test files and 4 testdata SQL files from PgSQL driver to
GaussDB driver
- Add `gaussdb_z_unit_feature_soft_time_test.go` (15 tests): soft time
create/update/delete, bool/int/datetime soft delete
- Add `gaussdb_z_unit_feature_with_test.go` (6 tests): With/WithAll ORM
relation queries, multiple dependency levels
- Add `gaussdb_z_unit_feature_scanlist_test.go` (9 tests): ScanList for
1:1, 1:N, N:N relation mapping
- Add 4 testdata SQL files for With relation tests
- **30 new test functions**, ~3,941 net new lines

## Test plan
- [x] `go build ./...` passes
- [x] `gofmt` and `gci` applied
- [x] No remaining `pgsql` references in new files
- [ ] Run full test suite against GaussDB instance

ref #4689

---------

Co-authored-by: John Guo <claymore1986@gmail.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

contrib/drivers/gaussdb/testdata/with_multiple_depends.sql

@@ -0,0 +1,30 @@
+
+CREATE TABLE table_a (
+    id SERIAL PRIMARY KEY,
+    alias varchar(255) DEFAULT ''
+);
+
+INSERT INTO table_a VALUES (1, 'table_a_test1');
+INSERT INTO table_a VALUES (2, 'table_a_test2');
+
+CREATE TABLE table_b (
+    id SERIAL PRIMARY KEY,
+    table_a_id integer NOT NULL,
+    alias varchar(255) DEFAULT ''
+);
+
+INSERT INTO table_b VALUES (10, 1, 'table_b_test1');
+INSERT INTO table_b VALUES (20, 2, 'table_b_test2');
+INSERT INTO table_b VALUES (30, 1, 'table_b_test3');
+INSERT INTO table_b VALUES (40, 2, 'table_b_test4');
+
+CREATE TABLE table_c (
+    id SERIAL PRIMARY KEY,
+    table_b_id integer NOT NULL,
+    alias varchar(255) DEFAULT ''
+);
+
+INSERT INTO table_c VALUES (100, 10, 'table_c_test1');
+INSERT INTO table_c VALUES (200, 10, 'table_c_test2');
+INSERT INTO table_c VALUES (300, 20, 'table_c_test3');
+INSERT INTO table_c VALUES (400, 30, 'table_c_test4');

contrib/drivers/gaussdb/testdata/with_tpl_user.sql

@@ -0,0 +1,4 @@
+CREATE TABLE IF NOT EXISTS %s (
+    id SERIAL PRIMARY KEY,
+    name varchar(45) NOT NULL
+);

contrib/drivers/gaussdb/testdata/with_tpl_user_detail.sql

@@ -0,0 +1,4 @@
+CREATE TABLE IF NOT EXISTS %s (
+    uid SERIAL PRIMARY KEY,
+    address varchar(45) NOT NULL
+);

contrib/drivers/gaussdb/testdata/with_tpl_user_scores.sql

@@ -0,0 +1,5 @@
+CREATE TABLE IF NOT EXISTS %s (
+    id SERIAL PRIMARY KEY,
+    uid integer NOT NULL,
+    score integer NOT NULL
+);