rust: bump rust-cpython version to 0.7.2 This version supports Python 3.12 while 0.7.1 did not.

rust: add Vfs trait This will allow for the use of multiple vfs like in the Python implementation, as well as hiding the details of the upcoming Python vfs wrapper to hg-core.

rust: use new revlog configs in all revlog opening code This centralizes the more complex logic needed for the upcoming code and creates stronger APIs with fewer booleans. We also reuse `RevlogType` where needed.

rust-revlog: don't try to open the data file if the index is empty This will cover the case where the data file is not present.

rust-revlog: add revlog-specific config objects These will be used by the upcoming Rust `InnerRevlog` to better centralize config information that is relevant to revlogs.

typing: add `from __future__ import annotations` to remaining source files Most of these look newer than when the original imports referenced in the previous commit were dropped, so these weren't covered by the backout. These were found with: hg files mercurial hgext hgext3rd -I '**.py' -X '**/thirdparty' \ | xargs grep -L 'from __future__ import annotations' All of the `__init__.py` files that finds are empty, so those were ignored and the rest manually edited.