budget: transaction-cache BudgetLine.getAvailableBudgetDict

Eventhough _getBudgetDict was cached, getAvailableBudgetDict also
calculates getCurrentBudget for each cell, which is also heavy.
10 jobs for master in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-Master

00:30:28

passed ERP5.PerformanceTest-Master

00:24:12

failed ERP5.UnitTest-Master

04:10:09

failed ERP5.UnitTest-Master.Medusa

02:15:51

passed SlapOS.Eggs.UnitTest-Master.Python2

00:24:58

failed SlapOS.Eggs.UnitTest-Master.Python3

00:09:35

passed SlapOS.Eggs.UnitTest-Master.Python2

00:34:19

passed SlapOS.Eggs.UnitTest-Master.Python2

passed SlapOS.Eggs.UnitTest-Master.Python2

failed SlapOS.Eggs.UnitTest-Master.Python3

00:10:54