Support GHC 9.0 and 9.2

[adamgundry]

In the process of making the plugin work on GHC 9.2 I seem to have accidentally made it work on GHC 9.0 as well. I've also added Github Actions support on GHC 9.0. Fixes #43 and fixes #79.

[philderbeast]

Could we say something in the readme about needing more iterations in GHC 9.0.1 than 9.2.0?

{-# OPTIONS_GHC -fconstraint-solver-iterations=6 #-}

[philderbeast]

I'm trying to compile flare-timing against this branch of the uom-plugin but hit a compile error when using convert compiling with stack and resolver: nightly-2021-06-24 (ghc-9.0.1), something I don't see with resolver: lts-11.22 (ghc-8.2.2):

https://github.com/BlockScope/flare-timing/blob/64a80131ae4b8bd6541bc663f20bc544fae600de/lang-haskell/latlng/library/Flight/LatLng/Alt.hs#L27-L31

stack build --stack-yaml=lang-haskell/stack-9.0.1.yaml
Warning: /.../stack-9.0.1.yaml: Unrecognized field in ProjectAndConfigMonoid: tested-with
flight-latlng> configure (lib)
flight-latlng> Configuring flight-latlng-0.1.0...
flight-latlng> build (lib)
flight-latlng> Preprocessing library for flight-latlng-0.1.0..
flight-latlng> Building library for flight-latlng-0.1.0..
flight-latlng> [ 3 of 13] Compiling Flight.LatLng.Alt
flight-latlng>
flight-latlng> /.../latlng/library/Flight/LatLng/Alt.hs:31:17: error:
flight-latlng>     • Couldn't match type: Data.UnitsOfMeasure.Internal.Pack
flight-latlng>                              (Data.UnitsOfMeasure.Internal.Unpack (Base "m"))
flight-latlng>                      with: Base "m"
flight-latlng>         arising from a use of ‘convert’
flight-latlng>     • In the expression: convert x
flight-latlng>       In an equation for ‘y’: y = convert x
flight-latlng>       In an equation for ‘toJSON’:
flight-latlng>           toJSON (Alt x)
flight-latlng>             = toJSON $ ViaQ (Alt y)
flight-latlng>             where
flight-latlng>                 y :: Quantity Double (Data.UnitsOfMeasure.Internal.MkUnit "m")
flight-latlng>                 y = convert x
flight-latlng>    |
flight-latlng> 31 |             y = convert x
flight-latlng>    |                 ^^^^^^^^^
flight-latlng>
flight-latlng> /.../latlng/library/Flight/LatLng/Alt.hs:36:23: error:
flight-latlng>     • Couldn't match type: Data.UnitsOfMeasure.Internal.Pack
flight-latlng>                              (Data.UnitsOfMeasure.Internal.Unpack (Base "m"))
flight-latlng>                      with: Base "m"
flight-latlng>         arising from a use of ‘convert’
flight-latlng>     • In the second argument of ‘($)’, namely ‘convert x’
flight-latlng>       In the first argument of ‘return’, namely ‘(Alt $ convert x)’
flight-latlng>       In a stmt of a 'do' block: return (Alt $ convert x)
flight-latlng>    |
flight-latlng> 36 |         return (Alt $ convert x)
flight-latlng>    |                       ^^^^^^^^^

I've made a reproduction of this failure in the Z module. I'll follow up with pull requests, one each for ghc-8.2.2 and ghc-9.0.1

[adamgundry]

Closing in favour of #93.