tree-optimization/107323 - loop distribution partition ordering issue

tree-optimization/107323 - loop distribution partition ordering issue

The following reverts part of the PR94125 fix which causes us to
use a bogus partition ordering after applying versioning for
alias to the testcase in PR107323.  Instead PR94125 is fixed by
appropriately considering to be merged SCCs when skipping edges
we want to ignore because of the alias versioning.

	PR tree-optimization/107323
	* tree-loop-distribution.cc (pg_unmark_merged_alias_ddrs):
	New function.
	(loop_distribution::break_alias_scc_partitions): Revert
	postorder save/restore from the PR94125 fix.  Instead
	make sure to not ignore edges from SCCs we are going to
	merge.

	* gcc.dg/tree-ssa/pr107323.c: New testcase.