Flip the default value of lukko flag in hackage-security

[Mikolaj]

Describe the feature request

Let's disable lukko by default on cabal master branch and if it works well, lets release cabal with this change and if it works well, let's make the flag flip also in hackage-security. Lukko is a workaround for a problem in base and it's hoped that it's not needed any more (and so it's not maintained as vigorously as when it was really needed).

Since cabal is the main (only?) user of https://github.com/haskell/hackage-security, let's discuss here this course of action, initially proposed by @Bodigrim in haskellari/lukko#39 (comment). The ticket also provides the context for this change.

One of related cabal tickets suggests some users work with the proposed setup (no lukko) successfully for many years now: #6657