merge: replace use of actions dict with mergeresult object There are still some places which can be improved by having a dedicated API, this patch for now make all users of actions dict go through the mergeresult object API. Differential Revision: https://phab.mercurial-scm.org/D8879

mergeresult: add sort argument to getactions() method This will be used in next patch. Differential Revision: https://phab.mercurial-scm.org/D8878

merge: pass mergeresult obj in merge._prefetchfiles() Differential Revision: https://phab.mercurial-scm.org/D8877

merge: pass mergeresult obj instead of actions in applyupdates() (API) This is similar to past 20 patches or so where we are replacing use of a bare actions dict with a dedicated mergeresult object. The goal is to have a dedicated powerful object instead of a dict while making the code more easier to understand. In past few patches, we have already simplified the code at some places using the newly introduced object. This patch does not updates applyupdates() to use the mergeresult object directly. That will be done in next patch to make things easier to review. Differential Revision: https://phab.mercurial-scm.org/D8876

merge: pass mergeresult obj instead of actions in _checkcollision() (API) The goal is to not use the actions dict and replace it with a rich mergeresult object. Differential Revision: https://phab.mercurial-scm.org/D8875

commitctx: directly update the touched and added set of files Instead of going through intermediate variable, we can simply use the ChangingFiles object. The object will take care of the consistency.

commitctx: directly updated the set of removed files The change is non-trivial so I made it in its own changeset.