Don't store repodata shards cache in top level rattler cache path

[pavelzw]

all ofd the shards(?) are a bit annoying. Would it be possible to move those to a subdirectory?

[baszalmstra]

Those are only the indexes! The shards are in the shards-v1 folder. I want to investigate using a sqlite database instead of seperate files as opening files is relatively slow.