Drop hex-text package (#7181)

The `hex-text` package is poorly maintained and we are only using
if for a single function that can be cargo culted into our code
base. The cargo culted function relies on the `base16-bytestring`
package but that is much more widely used and better maintained.

Author: erikd

cabal.project

@@ -87,8 +87,3 @@ allow-newer:
 --   flags: +force-build
 -- allow-newer: *:plutus-ledger-api
 -- allow-older: *:nothunks
-
-if impl (ghc >= 9.12)
-  allow-newer:
-    -- https://github.com/typeclasses/hex-text/issues/9
-    , hex-text:base

plutus-core/changelog.d/20250703_123351_erikd_drop_hex_text.md

@@ -0,0 +1,3 @@
+### Changed
+
+- Drop `hex-text` package in favor of `base16-bytestring`.

plutus-core/plutus-core.cabal

@@ -382,14 +382,14 @@ test-suite plutus-core-test
   build-depends:
     , aeson
     , base                             >=4.9     && <5
+    , base16-bytestring                ^>=1.0
     , bytestring
     , containers
     , data-default-class
     , extra
     , filepath
     , flat                             ^>=0.6
     , hedgehog
-    , hex-text
     , mmorph
     , mtl
     , plutus-core                      ^>=1.48

plutus-core/plutus-core/test/CBOR/DataStability.hs

@@ -33,10 +33,12 @@ where
 import PlutusCore.Data
 
 import Codec.Serialise (deserialise)
+import Data.ByteString.Base16 qualified as Base16 (decode)
+import Data.ByteString.Char8 (ByteString)
 import Data.ByteString.Lazy qualified as BSL (fromStrict, length)
 import Data.Maybe (fromJust)
 import Data.Text (Text)
-import Text.Hex (decodeHex)
+import Data.Text.Encoding qualified as Text (encodeUtf8)
 import Text.Printf (printf)
 
 import Test.Tasty
@@ -135,5 +137,8 @@ testData =
      )
    ]
 
-
-
+-- Lifted from the `hex-text` package which is being dropped because it
+-- is poorly maintained.
+decodeHex :: Text -> Maybe ByteString
+decodeHex txt =
+  either (const Nothing) Just (Base16.decode (Text.encodeUtf8 txt))