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

task_scheduler/go/db/task_test.go

 package db
 
 import (
         "bytes"
         "encoding/gob"
         "fmt"
         "sort"
         "testing"
         "time"
 
@@ skipping 512 matching lines @@
         _ = d.Process(invalid)
         for i := 0; i < 250; i++ {
                 _ = d.Process(serialized)
         }
 
         // Result should return error.
         result, err := d.Result()
         assert.Error(t, err)
         assert.Equal(t, 0, len(result))
 }