Merge #18621: script: Disallow silent bool -> CScript conversion

88884ee8d8dcd5303b20e54801b03f9631959c76 script: Disallow silent bool -> CScript conversion (MarcoFalke)

Pull request description:

  Makes nonsensical stuff like `ScriptToAsmStr(false,false);` a compile failure

ACKs for top commit:
  practicalswift:
    ACK 88884ee8d8dcd5303b20e54801b03f9631959c76
  laanwj:
    ACK 88884ee8d8dcd5303b20e54801b03f9631959c76
  promag:
    ACK 88884ee8d8dcd5303b20e54801b03f9631959c76.
  instagibbs:
    utACK 88884ee8d8dcd5303b20e54801b03f9631959c76
  jb55:
    ACK 88884ee8d8dcd5303b20e54801b03f9631959c76
  ryanofsky:
    Code review ACK 88884ee8d8dcd5303b20e54801b03f9631959c76

Tree-SHA512: 419d79c03b44a979c061b0540662928251ad68d53e65996bf370bb55ed1526ac7a22710cb7536c9954db5fec07bc312884bf8828f97a4ba180a5b07969a17f54

src/script/script.h

@@ -433,7 +433,7 @@ public:
         return ret;
     }
 
-    CScript(int64_t b)        { operator<<(b); }
+    explicit CScript(int64_t b) { operator<<(b); }
 
     explicit CScript(opcodetype b)     { operator<<(b); }
     explicit CScript(const CScriptNum& b) { operator<<(b); }