Use hackage-security library to extract `.cabal` files from the index

- [ ] Use library to extract .`cabal` files (and verify signatures once we introduce author signing; until that time this is just an optimization).
- [ ] Avoid creation of the `cabal`-specific tar index in favour of the index created by `hackage-security` (though note that the latter does not contain any information about `preferred-versions`). This should speed up `cabal update`.
- [ ] Once `cabal-install` only access the index through the security library, rename `00-index.tar` and co to `01-index.tar` (unless we can about older cabal's access?)

Start by tracing how cabal-install accesses the index and how the hackage-security library represents extracted .cabal files. Check the existing 00-index.tar handling and the missing preferred-versions information. Done means using the security library's index, avoiding the cabal-specific tar index, and resolving the compatibility-dependent archive rename.

Written by the indexing model from the issue text.