This commit makes lockfile version 4 the default version when Cargo
tries to write to a lockfile.
The lockfile version 4 has been stabilized since 1.78.0,
and will become default in 1.83.0.
the length of transition period is pretty similar as before.
One caveat is that in other output from Cargo,
e.g., `cargo metatada`, status messages,
`SourceID` will display in the v4 URL encoded format.
This shouldn't affect the majority of Rust users,
as `SourceId` representation should be opaque to them,
unless comparing `SourceId` across different version of toolchains.
This is for `cargo generate-lockfile` and when syncing the lockfile with
the manifest.
We still show it for `cargo update` because of `cargo update
--workspace`.
We hacked around this previously by filtering out the `num_pkgs==1` case
for single packages but this didn't help with workspaces.
