evolve: kill `--obsolete` and `--old-obsolete` flags for graft Evolve extension used to add the couple of flags to `hg graft` command for reasons I don't know but they were deprecated. For the functionality of `hg graft --old-obsolete`, we have `hg grab` now which can do that. One more reason to kill this is that we have logic to parse the graftstate, whereas in core, we are going to change how state files are read and write. Tweaked the tests a bit to use `hg grab` instead of these flags to make rest of the test output consistent. Replaced an entry of `hg graft -O` in doc by `hg grab`.

#require test-repo pyflakes

Copied from Mercurial core (60ee2593a270)

  $ cd "`dirname "$TESTDIR"`"

run pyflakes on all tracked files ending in .py or without a file ending
(skipping binary file random-seed)

  $ hg locate 'set:(**.py or grep("^#!.*python")) - removed()' 2>/dev/null \
  > | xargs pyflakes 2>/dev/null