bundle: introduce a "v3" spec This is a small update from "v2", we use the freshly out of experimental changelog version "03' format (alignment with bundle version is a coincidence) and we now bundle phases by default. We shall use v3 as the default bundle type later, when changegroup version '03' is a bit more established

bundle: add some phase boundary in the bundle type test case Same logic as the previous one, we want the tests to cover richer cases. It actually reveal a bug in `hg bundle foo.hg REMOTE` involving secret. So this is definitly not a bad idea.

bundle: expand the graph we us for bundletype/bundlespec tests We are about to test more things, especially phase bundling, so we need a graph a bit more complex than a single node. The test "code" was a bit simplified in the process, but no test-semantic changes were made.