changegroup: stop returning and recording added nodes in 'cg.apply' cg.apply used to returns the added nodes. Callers doesn't have a use for it anymore, remove the added node and stops recording it in the current operation. This information was added in the current release cycle so no extensions breakage should happens.

phases: remove trace of addednodes in the 'phase-heads' handling updatephases have no use of the 'addednodes' parameter since 50243c975fc2. However caller are still passing it for nothing, remove the parameter and remove computing of the added nodes in caller.

phases: test phases tracking at the transaction level Now that we have all tracking in place, the data in `tr.changes['phases']` dictionary should be correct and we should test it. It is a bit late in the cycle to discuss to add any public API (eg: hooks) that expose the data to the user, so we just add a small test extension displaying the data. It is enabled for the phases tests. New output have been manually checked for consistency.

phases: track phase changes from 'retractboundary' We adds new computation to find and record the revision affected by the boundary retraction. This add more complication to the function but this seems fine since it is only used in a couple of rare and explicit cases (`hg phase --force` and `hg qimport`). Having strong tracking of phase changes is worth the effort.