Tracking: Removal of old GHC versions

[wolfgangwalther]

According to our Deprecation Policy, we are going to drop a few GHC versions this cycle.

We'll want to keep all major versions from GHC 9.4 onwards:

• GHC 9.10 is the current Stackage LTS and will be our default soon.
• GHC 9.8 and 9.6 are the two latest major versions older than the default.
• GHC 9.6 is the version currently recommended by GHCup.
• GHC 9.4 is needed for pkgsStatic due to GHC >= 9.6 TemplateHaskell doesn't work in pkgsStatic #275304

Minor versions:

• GHC 9.4.7 haskell.compiler.ghc{947,964,965,966,981,982,983}: drop #440659
• GHC 9.6.3 haskell.compiler.ghc963: drop #440410
• GHC 9.6.4, 9.6.5, 9.6.6 haskell.compiler.ghc{947,964,965,966,981,982,983}: drop #440659
• GHC 9.8.1, 9.8.2, 9.8.3 haskell.compiler.ghc{947,964,965,966,981,982,983}: drop #440659
• GHC 9.10.1, 9.12.1
• 9.10.2 haskell.compiler.ghc{9102,9122}: drop #439323

Major source builds:

• GHCJS 8.10 haskell.compiler.ghcjs: remove at 8.10.7 #422342
• GHC 8.10 haskell.compiler.ghc{8107{,Binary},928}: drop #440794
• GHC 9.0 haskell.compiler.ghc902: remove at 9.0.2 #381265
• GHC 9.2 haskell.compiler.ghc{8107{,Binary},928}: drop #440794

Bindists:

• GHC 8.6 haskell.compiler.ghc865Binary: drop #440400
• GHC 8.10 haskell.compiler.ghc{8107{,Binary},928}: drop #440794
• GHC 9.0: Needed to bootstrap GHC 9.4.
• GHC 9.2: Needed to bootstrap GHC 9.6. Attempt in haskell.compiler.ghc924Binary: drop #440976
• GHC 9.6 Only possible after GHC 9.10.1 has been dropped.

cc @NixOS/haskell @emilazy

[wolfgangwalther]

Everything for 25.11 has been done here.