rpc, refactor: Add getblock_prevout

This change eliminates memory usage spike when compiling with Visual
Studio 2022 (at least in Cirrus CI environment).

Easy to review using
`git diff --color-moved-ws=allow-indentation-change --color-moved=dimmed-zebra`

Author: hebasto

src/rpc/blockchain.cpp

@@ -598,6 +598,29 @@ static CBlockUndo GetUndoChecked(BlockManager& blockman, const CBlockIndex* pblo
     return blockUndo;
 }
 
+const RPCResult getblock_vin{
+    RPCResult::Type::ARR, "vin", "",
+    {
+        {RPCResult::Type::OBJ, "", "",
+        {
+            {RPCResult::Type::ELISION, "", "The same output as verbosity = 2"},
+            {RPCResult::Type::OBJ, "prevout", "(Only if undo information is available)",
+            {
+                {RPCResult::Type::BOOL, "generated", "Coinbase or not"},
+                {RPCResult::Type::NUM, "height", "The height of the prevout"},
+                {RPCResult::Type::NUM, "value", "The value in " + CURRENCY_UNIT},
+                {RPCResult::Type::OBJ, "scriptPubKey", "",
+                {
+                    {RPCResult::Type::STR, "asm", "The asm"},
+                    {RPCResult::Type::STR, "hex", "The hex"},
+                    {RPCResult::Type::STR, "address", /*optional=*/true, "The Bitcoin address (only if a well-defined address exists)"},
+                    {RPCResult::Type::STR, "type", "The type (one of: " + GetAllOutputTypes() + ")"},
+                }},
+            }},
+        }},
+    }
+};
+
 static RPCHelpMan getblock()
 {
     return RPCHelpMan{"getblock",
@@ -657,26 +680,7 @@ static RPCHelpMan getblock()
                     {
                         {RPCResult::Type::OBJ, "", "",
                         {
-                            {RPCResult::Type::ARR, "vin", "",
-                            {
-                                {RPCResult::Type::OBJ, "", "",
-                                {
-                                    {RPCResult::Type::ELISION, "", "The same output as verbosity = 2"},
-                                    {RPCResult::Type::OBJ, "prevout", "(Only if undo information is available)",
-                                    {
-                                        {RPCResult::Type::BOOL, "generated", "Coinbase or not"},
-                                        {RPCResult::Type::NUM, "height", "The height of the prevout"},
-                                        {RPCResult::Type::NUM, "value", "The value in " + CURRENCY_UNIT},
-                                        {RPCResult::Type::OBJ, "scriptPubKey", "",
-                                        {
-                                            {RPCResult::Type::STR, "asm", "The asm"},
-                                            {RPCResult::Type::STR, "hex", "The hex"},
-                                            {RPCResult::Type::STR, "address", /*optional=*/true, "The Bitcoin address (only if a well-defined address exists)"},
-                                            {RPCResult::Type::STR, "type", "The type (one of: " + GetAllOutputTypes() + ")"},
-                                        }},
-                                    }},
-                                }},
-                            }},
+                            getblock_vin,
                         }},
                     }},
                 }},