Merge bitcoin/bitcoin#21745: refactor: Add missing includes in pubkey.cpp/pubkey.h

71c824e cleaned up and added missing "include" statements for pubkey.cpp and pubkey.h (William Bright)

Pull request description:

  #### Problem:
  Many symbols in the files were undefined and causing issues when I was working on building independent sections of the codebase. The hidden imports from the "secp256k1" library was a particular pain point.

  The other standard and missing includes are following best practices and will help with refactoring, build process and others.

  #### Changes:
  Clean up and declared imports/include for `pubkey.cpp` and `pubkey.h`

ACKs for top commit:
  jnewbery:
    utACK 71c824e
  laanwj:
    Code review ACK 71c824e

Tree-SHA512: bce605cfde24d8e3be82a596cabab7a8577fec0aef7c5e6f7a56603357046d8e8dea11ac8e3dbe79600550291be7784e35c7a55ebf40b46525b8949e4bedae96

Author: laanwj

src/pubkey.cpp

@@ -5,9 +5,16 @@
 
 #include <pubkey.h>
 
+#include <hash.h>
 #include <secp256k1.h>
+#include <secp256k1_extrakeys.h>
 #include <secp256k1_recovery.h>
 #include <secp256k1_schnorrsig.h>
+#include <span.h>
+#include <uint256.h>
+
+#include <algorithm>
+#include <cassert>
 
 namespace
 {

src/pubkey.h

@@ -12,7 +12,7 @@
 #include <span.h>
 #include <uint256.h>
 
-#include <stdexcept>
+#include <cstring>
 #include <vector>
 
 const unsigned int BIP32_EXTKEY_SIZE = 74;