uv-cache: bump simple cache version

It seems likely that we forgot to bump the version of the "simple" cache
in the 0.1.25 release. I'm still working on confirming it, but I figured
I'd get this bump up first.

The main problem here is that our "simple" cache is represented by
`rkyv`, and that in turn is tightly coupled to the representation of a
selection of data types in `uv`. Changing those data types without
bumping the cache version can result in cache deserialization errors
like this, or in the worst case, silent logic errors.

One possibility here is that the representation changed in a way that
permitted it to pass `rkyv` validation, but changed how the data itself
is interpreted. Our cache is robust with respect to `rkyv` validation
(if it fails, the cache will invalidate the entry and self-heal), but
being robust to higher level logical errors in interpretation of the
data is a much more significant challenge. Our best bet there is perhaps
some kind of checksum that we could do on top of `rkyv` validation (or
instead of it), and thus convert silent logical changes in how the data
is interpreted into failure modes that we're already robust to.

Fixes #2711

crates/uv-cache/src/lib.rs

@@ -598,7 +598,7 @@ impl CacheBucket {
             Self::FlatIndex => "flat-index-v0",
             Self::Git => "git-v0",
             Self::Interpreter => "interpreter-v0",
-            Self::Simple => "simple-v5",
+            Self::Simple => "simple-v6",
             Self::Wheels => "wheels-v0",
             Self::Archive => "archive-v0",
         }