[task scheduler] Move files from build_scheduler/ to task_scheduler/

task_scheduler/go/db/modified_tasks_test.go

 package db
 
 import (
         "testing"
         "time"
 
         assert "github.com/stretchr/testify/require"
 
         "go.skia.org/infra/go/testutils"
 )
@@ skipping 77 matching lines @@
                 assert.NoError(t, err)
                 oneId = id
         }
         _, err := m.StartTrackingModifiedTasks()
         assert.True(t, IsTooManyUsers(err))
 
         m.StopTrackingModifiedTasks(oneId)
         _, err = m.StartTrackingModifiedTasks()
         assert.NoError(t, err)
 }