scripted-diff: Use new FUZZ_TARGET macro everywhere

-BEGIN VERIFY SCRIPT-

  ren() { sed --regexp-extended -i "s|$1|$2|g" $(git grep -l --extended-regexp "$1"); }

  # Replace FUZZ_TARGET_INIT
  ren 'FUZZ_TARGET_INIT\((.+), (.+)\)' 'FUZZ_TARGET(\1, .init = \2)'

  # Delete unused FUZZ_TARGET_INIT
  sed -i -e '37,39d' src/test/fuzz/fuzz.h

-END VERIFY SCRIPT-

src/test/fuzz/block.cpp

@@ -23,7 +23,7 @@ void initialize_block()
     SelectParams(ChainType::REGTEST);
 }
 
-FUZZ_TARGET_INIT(block, initialize_block)
+FUZZ_TARGET(block, .init = initialize_block)
 {
     CDataStream ds(buffer, SER_NETWORK, INIT_PROTO_VERSION);
     CBlock block;