Merge #17439: refactor: Use proper MAX_SCRIPT_ELEMENT_SIZE constants consistently

cb9d830 test: Use proper MAX_SCRIPT_ELEMENT_SIZE (Hennadii Stepanov)
402ee70 refactor: Use proper MAX_SCRIPT_ELEMENT_SIZE const (Hennadii Stepanov)

Pull request description:

  This PR replaces well-known "magic" numbers with proper `MAX_SCRIPT_ELEMENT_SIZE` constants.

ACKs for top commit:
  practicalswift:
    ACK cb9d830 -- diff looks correct and change appears to be complete
  instagibbs:
    utACK bitcoin/bitcoin@cb9d830

Tree-SHA512: 5fa033275d6df7e35962c38bfdf09a7b5cd7ef2ccdd5e30a39ba47d0c21ac779a5559c23f5ef5bfd4293be0fc639e836a308bbedf0e34717e1eead983b389bbd

Author: MarcoFalke

src/script/descriptor.cpp

@@ -815,8 +815,8 @@ std::unique_ptr<DescriptorImpl> ParseScript(Span<const char>& sp, ParseScriptCon
             }
         }
         if (ctx == ParseScriptContext::P2SH) {
-            if (script_size + 3 > 520) {
-                error = strprintf("P2SH script is too large, %d bytes is larger than 520 bytes", script_size + 3);
+            if (script_size + 3 > MAX_SCRIPT_ELEMENT_SIZE) {
+                error = strprintf("P2SH script is too large, %d bytes is larger than %d bytes", script_size + 3, MAX_SCRIPT_ELEMENT_SIZE);
                 return nullptr;
             }
         }

test/functional/p2p_segwit.py

@@ -1116,7 +1116,7 @@ def test_max_witness_program_length(self):
         MAX_PROGRAM_LENGTH = 10000
 
         # This program is 19 max pushes (9937 bytes), then 64 more opcode-bytes.
-        long_witness_program = CScript([b'a' * 520] * 19 + [OP_DROP] * 63 + [OP_TRUE])
+        long_witness_program = CScript([b'a' * MAX_SCRIPT_ELEMENT_SIZE] * 19 + [OP_DROP] * 63 + [OP_TRUE])
         assert len(long_witness_program) == MAX_PROGRAM_LENGTH + 1
         long_witness_hash = sha256(long_witness_program)
         long_script_pubkey = CScript([OP_0, long_witness_hash])
@@ -1140,7 +1140,7 @@ def test_max_witness_program_length(self):
         test_witness_block(self.nodes[0], self.test_node, block, accepted=False)
 
         # Try again with one less byte in the witness program
-        witness_program = CScript([b'a' * 520] * 19 + [OP_DROP] * 62 + [OP_TRUE])
+        witness_program = CScript([b'a' * MAX_SCRIPT_ELEMENT_SIZE] * 19 + [OP_DROP] * 62 + [OP_TRUE])
         assert len(witness_program) == MAX_PROGRAM_LENGTH
         witness_hash = sha256(witness_program)
         script_pubkey = CScript([OP_0, witness_hash])