Move graphviz to new maintainer. Enable fgl-arbitrary. (#7199)

build-constraints.yaml

@@ -1334,7 +1334,9 @@ packages:
         - bounded-qsem
         - byteset
         - Clipboard
+        - fgl-arbitrary
         - gmail-simple
+        - graphviz
         - grouped-list
         - haskintex
         - HaTeX
@@ -2988,7 +2990,6 @@ packages:
 
     "Ivan Miljenovic <Ivan.Miljenovic@gmail.com> @ivan-m":
         - fgl
-        - graphviz
         - wl-pprint-text
         - servant-pandoc
 
@@ -8244,7 +8245,6 @@ skipped-tests:
     - cabal-helper
     - enum-text # https://github.com/commercialhaskell/stackage/issues/6794
     - ghc-exactprint # flaky fails with 'executable not found' & and runs around 15 minutes (so put here instead of expected-test-failures)
-    - graphviz
     - hpc-codecov # timeouts? https://github.com/commercialhaskell/stackage/issues/5976
     - ihaskell # Never finishes https://github.com/IHaskell/IHaskell/issues/1413
     - jsaddle # Never finishes without framebuffer https://github.com/ghcjs/jsaddle/issues/9
@@ -9252,7 +9252,6 @@ skipped-benchmarks:
     - fgl
     - fgl-arbitrary
     - graphviz
-    - graphviz
     - wl-pprint-text
     # @phadej
     - dlist-nonempty # criterion-1.3