Rework common stanzas in the cabal file generated by cabal init (haskell#11261)

* Reword common stanzas in the cabal file generated by `cabal init`

Following haskell#11231, this commit reworks the common stanzas present in the
cabal file generated by `cabal init`.

* Accept golden tests

* Don't insert rts options stanza imports for library

* Remove old common stanza

* Update golden tests

* Remove tests/fixtures from .gitignore

* Initial plan

* Remove -T and -Wcompat from the default flags

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: 2 people

cabal-install/src/Distribution/Client/Init/FileCreators.hs

@@ -74,15 +74,17 @@ writeProject (ProjectSettings opts pkgDesc libTarget exeTarget testTarget)
       writeReadme opts pkgDesc
 
       let pkgFields = mkPkgDescription opts pkgDesc
-          commonStanza = mkCommonStanza opts
+          extensionsStanza = mkExtensionsStanza opts
+          ghcOptionsStanza = mkGhcOptionsStanza opts
+          rtsOptionsStanza = mkRtsOptionsStanza opts
 
       libStanza <- prepareLibTarget opts libTarget
       exeStanza <- prepareExeTarget opts exeTarget
       testStanza <- prepareTestTarget opts testTarget
 
       (reusedCabal, cabalContents) <-
         writeCabalFile opts $
-          pkgFields ++ [commonStanza, libStanza, exeStanza, testStanza]
+          pkgFields ++ [extensionsStanza, ghcOptionsStanza, rtsOptionsStanza, libStanza, exeStanza, testStanza]
 
       when (null $ _pkgSynopsis pkgDesc) $
         message opts T.Warning "No synopsis given. You should edit the .cabal file and add one."