Make --no-tmp-comp-dir the default

Since Haddock uses GHC's no-code backend, using a temp directory for compilation results doesn't make sense anymore. Especially since it prevents reading of existing interface files and always triggers recompilation. This MR makes --no-tmp-comp-dir the default behavior and introduces a --tmp-comp-dir flag that reverts to the old default, just in case anyone needs it for some reason.