rust-hg-core: upgrade dependencies
This upgrades all dependencies to their latest version, except `clap` and `zstd`
whose latest versions do not support our minimum supported Rust version 1.48.0.
Same as for `rhg`, it contains security fix for `regex` which does not affect
us too much, but doesn't hurt, and the rest of the upgrades are there simply
to keep up.
Differential Revision: https://phab.mercurial-scm.org/D12358
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