rust: fix broken debug assertions These were caught by `clippy`. It appears no one uses the debug builds, which is how this wasn't caught before.

rust-narrow: fix loop that never loops This was caught by `clippy`. I guess the narrow tests leave something to be desired, since this previously only checked the first valid pattern.

rust: run `cargo clippy` These automatic fixes are good to have because they make the code more idiomatic and less surprising. The transform from `sort` -> `sort_unstable` is questionable, but this is only in a test, so it doesn't matter in our case.

rust: use `logging_timer` instead of `micro_timer` I am the author of `micro_timer`. I built it at the time because I couldn't find a crate that was simple to use and flexible to do function timing with. Turns out I just couldn't find it because crates.io's search isn't all that great, or maybe I didn't look hard enough. `logging_timer` is better in every way: - supports changing the logging level - supports start and end logging - supports intermediary messages - supports inline macros - supports formatting the output - better IDE/tree-sitter integration thanks to a more robust proc macro I also changed all uses to one-liners, so it's easier to copy-paste.

pathauditor: make _checkfs_exists a static method This fixes the bug detected by pytype where the auditor used in vfs.py may be a no-op auditor (vfs.py, line 398), which doesn't have the _checkfs_exists method.

merge: add mergeresult.mapaction to improve speed As a part of [hg update] we convert all [ACTION_CREATED] merge results into [ACTION_GET] actions, and that's slightly inefficient because every insertion pays the full cost of maintaining the [mergeresult] data structure up to date. This commit adds a function [mapaction], which is faster. (saves around 0.3s on a large update involving ~400k files)

merge: avoid dereferencing repo fields repeatedly

merge: skip syntactic path checks in [_checkunknownfile] We don't need to check the paths syntactically, since they are coming from diffing the revisions, so hopefully already checked on the way in. We still need to check what's on the filesystem, to avoid traversing the symlinks or subdirs, which we can't know about statically. Also, we use the directory audit to elide [isfileorlink], this removing ~all lstat calls from hg updates from-empty.

pathutil: use `finddirs_rev_noroot` instead of `parts` The benefit this brings is very tiny, if it's even there, since we still didn't get rid of the [parts] computation. It probably won't be worth it without the subsequent patch that adds one more use of [finddirs_rev_noroot]

pathutil: add the more efficient finddir iterator (to be used in subsequent commits)