gh-109162: Regrtest copies 'ns' attributes (#109168)

gh-109162: Regrtest copies 'ns' attributes (#109168)

* Regrtest.__init__() now copies 'ns' namespace attributes to
  Regrtest attributes. Regrtest match_tests and ignore_tests
  attributes have type FilterTuple (tuple), instead of a list.
* Add RunTests.copy(). Regrtest._rerun_failed_tests() now uses
  RunTests.copy().
* Replace Regrtest.all_tests (list) with Regrtest.first_runtests
  (RunTests).
* Make random_seed maximum 10x larger (9 digits, instead of 8).