dirstate: Skip no-op conversion in Rust DirstateMap::set_v1...
dirstate: Skip no-op conversion in Rust DirstateMap::set_v1
Now that the `DirstateItem` python class is implemented in Rust containing
a `DirstateEntry` value, use that value directly instead of reconstructing
it from v1 data.
Also rename from `set_v1` since dirstate-v1 data is not used anymore.
Differential Revision:
https://phab.mercurial-scm.org/D11487
