dirstate: fix parse_dirstate() to error out if NULL entry created Since 83f0e93ec34b "dirstate-item: move the C implementation to the same logic", dirstate_item_from_v1_data() gets more likely to return NULL, and the fuzzer crashes because of that.

rust: Remove EntryState::Unknown This enum variant represented the `state == '?'` case, which was used to represent the absence of a dirstate entry/item (and therefore of that entry’s state). Now that previous refactors have removed this use in the Python/Rust FFI APIs, the remaining uses can be removed by replacing `EntryState` by `Option<EntryState>` where appropriate, using `None` to represent the absence of an entry. Differential Revision: https://phab.mercurial-scm.org/D11465

dirstate: Remove the `state == ' '` special case Previously this was used to create a `DirstateItem` representing dirstate tree nodes that semantically don’t have an associated `DirtateItem`. This isn’t used anymore now that `dirstatemap.debug_iter` yields plain tuples. Differential Revision: https://phab.mercurial-scm.org/D11464

debugsate: Change debug_iter() to yield tuples instead of DirstateItem This removes the need for `DirstateItem` to support the `state == ' '` special case which represents dirstate tree nodes without an item. Differential Revision: https://phab.mercurial-scm.org/D11463

debugstate: Always call dirstatemap.debug_iter() … passing it a new `all` argument for the `--all` CLI option, instead of conditionally calling `.debug_iter()` or `.items()` This prepares for the next commit. Differential Revision: https://phab.mercurial-scm.org/D11462

rust: Make the fields of DirstateEntry private This is a first step toward making its internal structure equivalent to Python’s DirstateItem. Differential Revision: https://phab.mercurial-scm.org/D11461