Merge #19004: refactor: Replace const char* to std::string

c57f03ce17 refactor: Replace const char* to std::string (Calvin Kim)

Pull request description:

  Rationale: Addresses #19000
  Some functions should be returning std::string instead of const char*.
  This commit changes that.

  Main benefits/reasoning:

  1.  The functions never return nullptr, so returning a string makes code at call sites easier to review (reviewers don't have to read the source code to verify that a nullptr is never returned)
  2. All call sites convert to string anyway

ACKs for top commit:
  MarcoFalke:
    re-ACK c57f03ce17 (no changes since previous review) 🚃
  Empact:
    Fair enough, Code Review ACK c57f03ce17
  practicalswift:
    ACK c57f03ce17 -- patch looks correct
  hebasto:
    re-ACK c57f03ce17

Tree-SHA512: 9ce99bb38fe399b54844315048204cafce0f27fd8f24cae357fa7ac6f5d8094d57bbf5f5c1f5878a65f2d35e4a3f95d527eb17f49250b690c591c0df86ca84fd

src/script/standard.h

@@ -11,6 +11,8 @@
 
 #include <boost/variant.hpp>
 
+#include <string>
+
 
 static const bool DEFAULT_ACCEPT_DATACARRIER = true;
 
@@ -145,7 +147,7 @@ typedef boost::variant<CNoDestination, PKHash, ScriptHash, WitnessV0ScriptHash,
 bool IsValidDestination(const CTxDestination& dest);
 
 /** Get the name of a txnouttype as a C string, or nullptr if unknown. */
-const char* GetTxnOutputType(txnouttype t);
+std::string GetTxnOutputType(txnouttype t);
 
 /**
  * Parse a scriptPubKey and identify script type for standard scripts. If