Reorder Arbitrary instance definitions

Citing the GHC 9.0.1 changelog[1]:

  Breaking change: Template Haskell splices now act as separation points
  between constraint solving passes. It is no longer possible to use an
  instance of a class before a splice and define that instance after a
  splice. For example, this code now reports a missing instance for C
  Bool:

    ```
    class C a where foo :: a
    bar :: Bool
    bar = foo
    $(return [])
    instance C Bool where foo = True
    ```

In other words, code order matters in Template Haskell files, which
breaks the Haskell test build with GHC >= 9.0.1. Fix this by reordering
various Arbitrary instances so that they are defined before being used.

Also the Arbitrary instance for IAllocatorParams was silently acting as
a generic instance for (Container JSValue), providing instances for
DiskParams, HypervisorState and DiskState as well. Change the Arbitrary
instance declaration to Arbitrary (Container JSValue) to better reflect
its generic purpose.

[1] https://downloads.haskell.org/ghc/9.0.1/docs/html/users_guide/9.0.1-notes.html#highlights

Signed-off-by: Apollon Oikonomopoulos <apoikos@dmesg.gr>

test/hs/Test/Ganeti/Objects.hs

@@ -93,8 +93,14 @@ instance Arbitrary (Container DataCollectorConfig) where
 instance Arbitrary BS.ByteString where
   arbitrary = genPrintableByteString
 
+instance Arbitrary a => Arbitrary (Private a) where
+  arbitrary = Private <$> arbitrary
+
 $(genArbitrary ''PartialNDParams)
 
+instance Arbitrary (Container J.JSValue) where
+  arbitrary = return $ GenericContainer Map.empty
+
 instance Arbitrary Node where
   arbitrary = Node <$> genFQDN <*> genFQDN <*> genFQDN
               <*> arbitrary <*> arbitrary <*> arbitrary <*> genFQDN
@@ -297,10 +303,6 @@ genDisk = genDiskWithChildren 3
 -- validation rules.
 $(genArbitrary ''PartialISpecParams)
 
--- | FIXME: This generates completely random data, without normal
--- validation rules.
-$(genArbitrary ''PartialIPolicy)
-
 $(genArbitrary ''FilledISpecParams)
 $(genArbitrary ''MinMaxISpecs)
 $(genArbitrary ''FilledIPolicy)
@@ -309,6 +311,10 @@ $(genArbitrary ''FilledNDParams)
 $(genArbitrary ''FilledNicParams)
 $(genArbitrary ''FilledBeParams)
 
+-- | FIXME: This generates completely random data, without normal
+-- validation rules.
+$(genArbitrary ''PartialIPolicy)
+
 -- | No real arbitrary instance for 'ClusterHvParams' yet.
 instance Arbitrary ClusterHvParams where
   arbitrary = return $ GenericContainer Map.empty
@@ -331,18 +337,12 @@ instance Arbitrary OsParams where
 instance Arbitrary Objects.ClusterOsParamsPrivate where
   arbitrary = (GenericContainer . Map.fromList) <$> arbitrary
 
-instance Arbitrary a => Arbitrary (Private a) where
-  arbitrary = Private <$> arbitrary
-
 instance Arbitrary ClusterOsParams where
   arbitrary = (GenericContainer . Map.fromList) <$> arbitrary
 
 instance Arbitrary ClusterBeParams where
   arbitrary = (GenericContainer . Map.fromList) <$> arbitrary
 
-instance Arbitrary IAllocatorParams where
-  arbitrary = return $ GenericContainer Map.empty
-
 $(genArbitrary ''Cluster)
 
 instance Arbitrary ConfigData where

test/hs/Test/Ganeti/Query/Language.hs

@@ -59,6 +59,9 @@ import Ganeti.Query.Language
 instance Arbitrary (Filter FilterField) where
   arbitrary = genFilter
 
+instance Arbitrary FilterRegex where
+  arbitrary = genName >>= mkRegex -- a name should be a good regex
+
 -- | Custom 'Filter' generator (top-level), which enforces a
 -- (sane) limit on the depth of the generated filters.
 genFilter :: Gen (Filter FilterField)
@@ -97,9 +100,6 @@ $(genArbitrary ''QueryTypeLuxi)
 
 $(genArbitrary ''ItemType)
 
-instance Arbitrary FilterRegex where
-  arbitrary = genName >>= mkRegex -- a name should be a good regex
-
 $(genArbitrary ''ResultStatus)
 
 $(genArbitrary ''FieldType)