Make lukko flag automatic and off by default

The lukko package (https://hackage.haskell.org/package/lukko)
was meant to be a temporary workaround, and relevant improvements
have been long accessible from base:GHC.IO.Handle.Lock.

As suggested at haskellari/lukko#39 (comment),
let's switch the default value of the lukko flag of cabal-install
from True to False. Additionally, to be on the safe side, we make it
an automatic one, so that if things go terribly wrong a Hackage revision
could sort it back.

The same change has been implemented for the hackage-security package
sometime ago in haskell/hackage-security#322,
and there seems to be no complaints.

Author: Bodigrim

cabal-install/cabal-install.cabal

@@ -36,8 +36,8 @@ Flag native-dns
 
 Flag lukko
   description:  Use @lukko@ for file-locking
-  default:      True
-  manual:       True
+  default:      False
+  manual:       False
 
 flag git-rev
   description: include Git revision hash in version

changelog.d/pr-11003.md

@@ -0,0 +1,8 @@
+---
+synopsis: Make lukko flag automatic and off by default
+packages: [cabal-install]
+prs: 11003
+issues: 10724
+---
+
+Make `lukko` flag automatic and off by default, using file locking facilities from `base:GHC.IO.Handle.Lock` and not from the `lukko` package. The change is not expected to affect anyone detrimentally, but one can set the flag on in their configuration to restore the previous behaviour.