Allow building with GHC 9.2, update CI

[sjakobi]

This is still blocked on a large number of dependencies.

Incantation as of 2022-03-14:

cabal build --allow-newer=snap-server:base,io-streams-haproxy:base,snap-server:bytestring,snap-server:attoparsec,websockets-snap:bytestring,snap-server:time,io-streams-haproxy:attoparsec,io-streams-haproxy:bytestring

Upstream issues:

• [x] https://github.com/haskell/aeson/issues/885.
• [x] https://github.com/snapframework/snap-core/issues/311 (needs release)
• [x] https://github.com/snapframework/snap-server/issues/142
• [x] https://github.com/snapframework/io-streams-haproxy/pull/21
• [x] https://github.com/snapframework/snap-server/issues/148
• [x] https://github.com/snapframework/io-streams-haproxy/issues/25

[sjakobi]

I already get a clean build with GHC 9.2 when I use Head Hackage:

--- a/cabal.project
+++ b/cabal.project
@@ -1,2 +1,13 @@
 packages: "."
 flags: +buildexamples
+
+repository head.hackage.ghc.haskell.org
+   url: https://ghc.gitlab.haskell.org/head.hackage/
+   secure: True
+   key-threshold: 3
+   root-keys:
+       f76d08be13e9a61a377a85e2fb63f4c5435d40f8feb3e12eb05905edb8cdea89
+       26021a13b401500c8eb2761ca95c61f2d625bfef951b939a8124ed12ecf07329
+       7541f32a4ccca4f97aea3b22f5e593ba2c0267546016b992dfadcd2fe944e55d
+
+active-repositories: hackage.haskell.org, head.hackage.ghc.haskell.org:override

Therefore I've already pushed a matching Hackage revision: https://hackage.haskell.org/package/threepenny-gui-0.9.1.0/revisions/

[sjakobi]

I already get a clean build with GHC 9.2 when I use Head Hackage:

https://github.com/HeinrichApfelmus/threepenny-gui/issues/261 explains the "cleanliness". ;)

[sjakobi]

Superseded by #267