Switch from template-haskell to template-haskell-lift

[TeofilC]

We switch our dependency on template-haskell to a dependency on template-haskell-lift. This smaller library is more stabler and if we can remove the template-haskell dependency from all boot libraries then template-haskell will be much easier to re-install since it no longer needs to be in GHC's dependency closure.

It also lets us drop a lot of compatibility CPP.

For more information see the GHC proposal that introduced this library: ghc-proposals/ghc-proposals#696

template-haskell-lift is not compatible with versions of GHC before 9.10, so support for earlier versions would either need to be dropped, or we would need to add some CPP.

This GHC MR tests this PR against GHC-HEAD: https://gitlab.haskell.org/ghc/ghc/-/merge_requests/14978

[Bodigrim]

We strive for new releases to be backportable to older GHC major series, which do not yet have template-haskell-lift as a boot library. To keep it possible, I imagine you need something like

if impl(ghc>9.15)
  build-depends: template-haskell-lift
else 
  build-depends: template-haskell 

[TeofilC]

Good point. template-haskell-lift itself is buildable with older major versions (where it just re exports tenplate-haskell) but unless we backport it as a boot library to those versions then indeed you wouldn't be able to use the new bytestring as a boot library.

I'll implement what you suggest

[Bodigrim]

@TeofilC please rebase.

[Bodigrim]

@TeofilC could you please raise a draft GHC MR, which updates bytestring submodule to your commit? Otherwise I cannot test it.