Add fancier trace debugging functions to Hasura.Prelude

## Suggestion: Add fancier trace debugging functions to `Hasura.Prelude`

This PR adds two trace functions, `ltrace` and `ltraceM`, which use the `pretty-simple` package to `show` the input with nice formatting and colors for ease of reading (and comparing using diff tools such as `meld` or `vim-diff`).

I've also added warning pragmas to the functions, which means:
1. Traces will not be left in code, as CI builds with -Werror
2. Developers will have to change the `ghc-options` to `-Wwarn` in their `cabal.project.local` settings to use these functions

### Example

Usage:

```hs
selectFunctionAggregate ... = ... do
  ltraceM "functionInfo" function
  ...
```

Output to terminal looks like this:

<img width="524" alt="Screen Shot 2021-08-12 at 10 33 24" src="https://user-images.githubusercontent.com/8547573/129158878-4a5e96ba-30a5-452c-8f33-9eb4b2cc5e2a.png">

### Dependencies

Requires adding the following dependencies:
  - prettyprinter-ansi-terminal-1.1.2 (BSD2)
  - pretty-simple-4.0.0.0 (BSD3)

Question: what is the process for adding new dependencies? How does decisions on this matter happen?

https://github.com/hasura/graphql-engine-mono/pull/2075

GitOrigin-RevId: 490b0f0ca595da319b43e92e190ba50c0b132cd5

cabal.project.freeze

@@ -281,9 +281,11 @@ constraints: any.Cabal ==3.2.0.0,
              any.postgresql-libpq ==0.9.4.3,
              postgresql-libpq -use-pkg-config,
              any.pretty ==1.1.3.6,
+             any.pretty-simple ==4.0.0.0,
              any.pretty-show ==1.10,
              any.prettyprinter ==1.7.0,
              prettyprinter -buildreadme,
+             prettyprinter-ansi-terminal ==1.1.2,
              any.primitive ==0.7.1.0,
              any.primitive-extras ==0.8,
              any.primitive-unlifted ==0.1.3.0,

server/graphql-engine.cabal

@@ -131,6 +131,7 @@ library
                      , pg-client
                      , postgresql-binary
                      , postgresql-libpq
+                     , pretty-simple
                      , process
                      , profunctors
                      , retry

server/src-lib/Hasura/Prelude.hs

@@ -19,6 +19,9 @@ module Hasura.Prelude
   , hoistMaybe
   , hoistEither
   , tshow
+  -- * Trace debugging
+  , ltrace
+  , ltraceM
   -- * Efficient coercions
   , coerce
   , findWithIndex
@@ -96,8 +99,11 @@ import qualified Data.Hashable               as H
 import qualified Data.Text                   as T
 import qualified Data.Text.Encoding          as TE
 import qualified Data.Text.Encoding.Error    as TE
+import qualified Data.Text.Lazy              as TL
 import qualified GHC.Clock                   as Clock
 
+import           Debug.Trace                 (trace, traceM)
+import qualified Text.Pretty.Simple          as PS
 
 alphabet :: String
 alphabet = ['a'..'z'] ++ ['A'..'Z']
@@ -233,3 +239,15 @@ instance (Hashable a) => Hashable (Seq a) where
 -- as @foldMap id@, per the documentation in @Data.Foldable@.
 fold' :: (Monoid m, Foldable t) => t m -> m
 fold' = foldMap' id
+
+-- Fancy trace debugging
+
+-- | Labeled, prettified traceShowId
+ltrace :: Show a => String -> a -> a
+ltrace lbl x = trace (lbl <> ": " <> TL.unpack (PS.pShow x)) x
+{-# warning ltrace "ltrace left in code" #-}
+
+-- | Labeled, prettified traceShowM
+ltraceM :: Applicative m => Show a => String -> a -> m ()
+ltraceM lbl x = traceM (lbl <> ": " <> TL.unpack (PS.pShow x))
+{-# warning ltraceM "ltraceM left in code" #-}