dirstate: move opendirstatefile to dirstatemap As part of moving the dirstate storage logic to another class, let's move opendirstatefile to dirstatemap. This will allow extensions to replace the pending abstraction. Future patches will move the consumers of _opendirstatefile into dirstatemap as well. Differential Revision: https://phab.mercurial-scm.org/D757

dirstate: move _copymap to dirstatemap As part of moving all dirstate storage to a new class, let's move the copymap onto that class. In a future patch this will let us move the read/write functions to the dirstatemap class, and for extensions this lets us replace the copy storage with alternative storage. Differential Revision: https://phab.mercurial-scm.org/D756

dirstate: move _dirs to dirstatemap As part of moving the dirstate storage logic to a new class, lets move the _dirs computation onto the class so extensions can replace it with a persisted index of directories. Differential Revision: https://phab.mercurial-scm.org/D755