Merge #3987

3987: [ADP-3063] Remove `ConnectionPool` r=HeinrichApfelmus a=HeinrichApfelmus

### Overview

This task is about removing the `ConnectionPool` type and `withConnectionPool` function.

Historically, the `ConnectionPool` was an attempt to enable concurrent reading from a database file. However, the present state of the code is that only a single connection is ever used per database file.

### Comments

* This fixes an issue where `runQuery` would close and open the database connection all the time — instead of working with a `pool :: ConnectionPool`, this function would work with a `fp :: FilePath`.

### Issue number

ADP-3063


Co-authored-by: Heinrich Apfelmus <heinrich.apfelmus@iohk.io>
Co-authored-by: paolino <paolo.veronelli@gmail.com>

lib/wallet/bench/db-bench.hs

@@ -58,7 +58,7 @@ import Cardano.BM.Data.Tracer
 import Cardano.BM.Setup
     ( setupTrace_, shutdown )
 import Cardano.DB.Sqlite
-    ( ConnectionPool, SqliteContext (..) )
+    ( SqliteContext (..) )
 import Cardano.Mnemonic
     ( EntropySize, SomeMnemonic (..), entropyToMnemonic, genEntropy )
 import Cardano.Startup
@@ -790,9 +790,6 @@ instance NFData (DBLayer m s) where
 instance NFData SqliteContext where
     rnf _ = ()
 
-instance NFData ConnectionPool where
-    rnf _ = ()
-
 testCp :: WalletBench
 testCp = snd $ initWallet block0 initDummySeqState
 

lib/wallet/cardano-wallet.cabal

@@ -169,7 +169,6 @@ library
     , quiet
     , random
     , random-shuffle
-    , resource-pool
     , retry
     , safe
     , safe-money