chore: enable GHC NumericUnderscores language extension

The `_` character between numeric literals improve their readablity.

Signed-off-by: Taimoor Zaeem <taimoorzaeem@gmail.com>

test/observability/ObsHelper.hs

@@ -206,7 +206,7 @@ waitForObs (ObsChan orig copy) t msg f =
     -- duplicate the provided channel and construct wairFor function binding both channels
     -- accumulate effecful computation results into a list for specified time
     takeUntilTimeout t' = fmap reverse . accumulateUntilTimeout t' (flip (:)) []
-    decisecond = 100000
+    decisecond = 100_000
 
 obsDiagMessage :: Observation -> Text
 obsDiagMessage = \case

test/observability/Observation/SchemaCacheSpec.hs

@@ -46,4 +46,4 @@ spec = describe "Server started with metrics enabled" $ do
         waitFor (1 * sec) "SchemaCacheQueriedObs" $ \x -> [ o | o@SchemaCacheQueriedObs{} <- pure x ]
         waitFor (1 * sec) "SchemaCacheLoadedObs" $ \x -> [ o | o@SchemaCacheLoadedObs{} <- pure x ]
   where
-    sec = 1000000
+    sec = 1_000_000

test/spec/SpecHelper.hs

@@ -250,7 +250,7 @@ planCost :: SResponse -> Float
 planCost resp =
   let res = simpleBody resp ^? nth 0 . key "Plan" . key "Total Cost" in
   -- big value in case parsing fails
-  fromMaybe 1000000000.0 $ unbox =<< res
+  fromMaybe 1_000_000_000.0 $ unbox =<< res
   where
     unbox :: JSON.Value -> Maybe Float
     unbox (JSON.Number n) = Just $ toRealFloat n