ERP5Type: make TempBase use TemporaryDocumentMixin

Now that TemporaryDocumentMixin and TempBase implementation details have
been made consistent, there's no reason to duplicate code.

This also make TempBase uses TemporaryDocumentMixin of __setstate__, so
TempBase have more sane behaviour when being pickled.
2 jobs for feat/accounting_view_item in 0 seconds
Status Job ID Name Coverage
  External
passed ERP5.CodingStyleTest-TestRunner2

06:32:30

failed ERP5.UnitTest-TestRunner2

10:31:02