Drop ghc support for 8.6.4, 8.10.2, 8.10.3, 8.10.4

[jneira]

• Following the incoming ghc deprecation policy ghc support deprecation schedule #2168
• Include the bump of ghc-lib* versions to 8.10.7 and the use of 8.10.7 in tests and benchmarks
• Update hackage index to 2021-09-16T07:00:23Z

[pepeiborra]

Nice!

[July541]

Should we change the default stack.yaml(https://github.com/haskell/haskell-language-server/blob/master/stack.yaml) to 8.10.7?

[jneira]

Should we change the default stack.yaml(https://github.com/haskell/haskell-language-server/blob/master/stack.yaml) to 8.10.7?

good catch! i forgot to update it, thanks!

[Ailrun]

LGTM! However, this PR cannot be automatically merged, as

1. This PR changes CI config
2. This PR adds/removes some CI entries, so branch protection rule should be updated

[jneira]

/rerun-workflow Testing

[jneira]

• Changed branch protection rules, we have to update rest of prs
  EDIT: i've updated a bunch of them

[anka-213]

Is there any specific reason why 8.8.3 is still here? Will it be removed at a later point or is it meant to stay for longer or was it simply forgotten?

[jneira]

Is there any specific reason why 8.8.3 is still here? Will it be removed at a later point or is it meant to stay for longer or was it simply forgotten?

hi, we keep it following the deprecation policy discussed in #2168, it says we will keep the last 2 minor versions for relatively recent ghc versions

[anka-213]

Ah, I see! I missed that part! Thanks!

[anka-213]

I was looking at the table which said:

condition	removed ghc versions	supported ghc versions
after next release 1.4.0 with 8.10.7	8.10.4, 8.10.3, 8.10.2, 8.8.3, 8.6.4	9.0.1 (partial), 8.10.7, 8.10.6, 8.10.5, 8.8.4, 8.6.5

which is what confused me. (ghc-8.8.3 is under the removed section)

[jneira]

oh, yeah, that was the initial proposal but it has changed due the discussion, we have to write down the definitive one with a new table