Migrate/remove old patches

• Migrate the patches for doctest, free, persistent, and yesod-core to the latest versions on Hackage.
• Remove the patches for Cabal, bytes, cabal-doctest, ghc-paths, hsc2hs, polyparse, singleton-nats, tar, yaml, and zlib, as more recent versions of these packages (that support GHC 8.8 and HEAD) are now available on Hackage.

I opted not to remove the th-desugar-1.9/singletons-2.5.1 patches for now, even though they are not the latest Hackage releases, since upgrading them can be a nontrivial process (similar to the primitive-0.6/-0.7 situation).