Merge bitcoin/bitcoin#26710: refactor: Fix performance-for-range-copy in headers

48033d4 clang-tidy: Fix `performance-for-range-copy` in headers (Hennadii Stepanov)

Pull request description:

  Split from bitcoin/bitcoin#26705 as was requested in bitcoin/bitcoin#26705 (comment).

  To test this PR, consider applying a diff as follows:
  ```diff
  --- a/src/.clang-tidy
  +++ b/src/.clang-tidy
  @@ -12,17 +12,9 @@ readability-redundant-declaration,
   readability-redundant-string-init,
   '
   WarningsAsErrors: '
  -bugprone-argument-comment,
  -bugprone-use-after-move,
  -misc-unused-using-decls,
  -modernize-use-default-member-init,
  -modernize-use-nullptr,
   performance-for-range-copy,
  -performance-move-const-arg,
  -performance-unnecessary-copy-initialization,
  -readability-redundant-declaration,
  -readability-redundant-string-init,
   '
   CheckOptions:
    - key: performance-move-const-arg.CheckTriviallyCopyableMove
      value: false
  +HeaderFilterRegex: '.'
  ```

ACKs for top commit:
  MarcoFalke:
    review ACK 48033d4

Tree-SHA512: eaf7a0e9b4fdc4ce788f78e5675632f3c278fc24bee2434874cbabc3e25ad7059b0c53ab7834908e901872d5afee08acba860542b03454c09fe129be6ad03f09

Author: MarcoFalke

src/psbt.h

@@ -178,7 +178,7 @@ void SerializeHDKeypath(Stream& s, KeyOriginInfo hd_keypath)
 template<typename Stream>
 void SerializeHDKeypaths(Stream& s, const std::map<CPubKey, KeyOriginInfo>& hd_keypaths, CompactSizeWriter type)
 {
-    for (auto keypath_pair : hd_keypaths) {
+    for (const auto& keypath_pair : hd_keypaths) {
         if (!keypath_pair.first.IsValid()) {
             throw std::ios_base::failure("Invalid CPubKey being serialized");
         }