rust: Remove the `rustext.parsers` module
It only exported Rust implementations of the parse_dirstate and pack_dirtate
functions, which are only used (anymore) when Rust is not enabled.
fakedirstatewritetime.py was detecting the presence of `rustext.parsers`
but what it really wants to know is whether the Rust implementation of
`dirstatemap` is used. This changes it to detect `rustext.dirstate` instead.
Differential Revision: https://phab.mercurial-scm.org/D11459
edition = "2018"
max_width = 79
wrap_comments = true
error_on_line_overflow = true