tortoisehg intentionally wants to back-date the Mercurial build,
and some of the features we've added to the Mercurial build won't work
correctly under hg 5.6.
The Rust extensions provide speedups for core Mercurial functionality.
We should start building with them.
They're only CI-tested on Linux, so they're disabled for non-Linux
platforms for now by default.
###### Motivation for this change
Update to latest upstream version
###### Things done
* [ ] Tested using sandboxing ([nix.useSandbox](http://nixos.org/nixos/manual/options.html#opt-nix.useSandbox) on NixOS, or option `sandbox` in [`nix.conf`](http://nixos.org/nix/manual/#sec-conf-file) on non-NixOS linux)
* Built on platform(s)
* [x] NixOS
* [ ] macOS
* [ ] other Linux distributions
* [ ] Tested via one or more NixOS test(s) if existing and applicable for the change (look inside [nixos/tests](https://github.com/NixOS/nixpkgs/blob/master/nixos/tests))
* [ ] Tested compilation of all pkgs that depend on this change using `nix-shell -p nix-review --run "nix-review wip"`
* [x] Tested execution of all binary files (usually in `./result/bin/`)
* [ ] Determined the impact on package closure size (by running `nix path-info -S` before and after)
* [ ] Ensured that relevant documentation is up to date
* [x] Fits [CONTRIBUTING.md](https://github.com/NixOS/nixpkgs/blob/master/.github/CONTRIBUTING.md).
The upstream recommended minimum length for db_key_base is 30 bytes,
which our option descriptions repeated. Recently, however, upstream
has, in many places, moved to using aes-256-gcm, which requires a key
of exactly 32 bytes. To allow for shorter keys, the upstream code pads
the key in some places. However, in many others, it just truncates the
key if it's too long, leaving it too short if it was to begin
with. This adds a patch that fixes this and updates the descriptions
to recommend a key of at least 32 characters.
See https://gitlab.com/gitlab-org/gitlab/-/merge_requests/53602
`buildGoModule` and `buildGoPackage` by default inherit the `platforms`
from go. That seems better than explicitly configuring `platforms.all`.
There are also many packages that specify 'linux + darwin' - this is
even suggested in the documentation. We might also want to update those,
but let's do the noncontroversial change first.
