evolve: use phases.new-commit config to retain phase information (issue5720) Since the previous patches replaced the use of graftstate with evolvestate and we don't graft anymore on evolve --continue, we have now the capability to fix underlying bugs. This patch makes sure we use the phases.new-commit config to make a new commit of the same phase as that of the predecessor. Tests added in the previous patch shows the bug being fixed.

tests: add a test demonstarting lose of phase in `hg evolve` This patch adds a new test file which demonstrates the lose of phase information when hg evolve command runs into conflict. This is algo bug5720. The upcoming patch will fix it. A new test file is added as existing test files serve their own purpose and are already cluttered.