configitems: move the default values to the registrar decorator The exthelper refactoring of configitems stopped registering dynamicdefault for everything, which in turn causes a lot of warnings about mismatched defaults. There are a few stragglers- I didn't fix topic-mode because I wasn't sure what the default should be, and the alias for odiff was explicitly given a default for compatibility.

#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