Unistore Chore: add inocuous preparative changes for otel-based db observability (#94473)

add inocuous preparative changes for otel tracing

pkg/storage/unified/sql/db/dbimpl/driver_test.go

@@ -0,0 +1,95 @@
+package dbimpl
+
+import (
+	"context"
+	"database/sql"
+	"database/sql/driver"
+	"sync"
+)
+
+var _ driver.Driver = driverWithoutIsolationLevel{}
+var _ driver.Driver = driverWithIsolationLevel{}
+
+const (
+	driverWithoutIsolationLevelName = "test driver without isolation levels"
+	driverWithIsolationLevelName    = "test driver with isolation levels"
+)
+
+var registerTestDriversOnce sync.Once
+
+func registerTestSQLDrivers() {
+	registerTestDriversOnce.Do(func() {
+		sql.Register(driverWithoutIsolationLevelName, driverWithoutIsolationLevel{})
+		sql.Register(driverWithIsolationLevelName, driverWithIsolationLevel{})
+	})
+}
+
+type (
+	// without isolation level
+
+	driverWithoutIsolationLevel struct{}
+	connWithoutIsolationLevel   struct{}
+
+	// with isolation level
+
+	driverWithIsolationLevel struct{}
+	connWithIsolationLevel   struct {
+		connWithoutIsolationLevel
+	}
+
+	// common
+
+	testStmt    struct{}
+	testTx      struct{}
+	testResults struct{}
+	testRows    struct{}
+)
+
+// driver.Driver
+
+func (driverWithoutIsolationLevel) Open(name string) (driver.Conn, error) {
+	return connWithoutIsolationLevel{}, nil
+}
+
+func (driverWithIsolationLevel) Open(name string) (driver.Conn, error) {
+	return connWithIsolationLevel{}, nil
+}
+
+// driver.Conn
+
+func (connWithoutIsolationLevel) Prepare(query string) (driver.Stmt, error) {
+	return testStmt{}, nil
+}
+func (connWithoutIsolationLevel) Close() error {
+	return nil
+}
+func (connWithoutIsolationLevel) Begin() (driver.Tx, error) {
+	return testTx{}, nil
+}
+
+func (connWithIsolationLevel) BeginTx(context.Context, driver.TxOptions) (driver.Tx, error) {
+	return testTx{}, nil
+}
+
+// driver.Stmt
+
+func (testStmt) Close() error                                    { return nil }
+func (testStmt) NumInput() int                                   { return 0 }
+func (testStmt) Exec(args []driver.Value) (driver.Result, error) { return testResults{}, nil }
+func (testStmt) Query(args []driver.Value) (driver.Rows, error)  { return testRows{}, nil }
+
+// driver.Tx
+
+func (testTx) Commit() error   { return nil }
+func (testTx) Rollback() error { return nil }
+
+// driver.Results
+
+func (testResults) LastInsertId() (int64, error) { return 1, nil }
+func (testResults) RowsAffected() (int64, error) { return 1, nil }
+
+// driver.Rows
+
+func (testRows) Columns() []string              { return nil }
+func (testRows) Close() error                   { return nil }
+func (testRows) Next(dest []driver.Value) error { return nil }