feat(depotfmt): Check & format Rust code with rustfmt r/3792

The rustfmt configuration of the depot is moved to `rustfmt.toml` (it
is recognised more reliably from this path than from the hidden
.rustfmt.toml).

Nested configuration is theoretically possible, but detection of
nested config files is flaky. Paths with nested config files need to
be disabled in the top-level check (I've excluded my user directory).

Change-Id: I385ce3ef529bda28fac03bfba86fc204c81b8a61
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5241
Tested-by: BuildkiteCI
Reviewed-by: grfn <grfn@gws.fyi>

0 files changed, 0 insertions, 0 deletions