Merge bitcoin/bitcoin#22951: consensus: move amount.h into consensus

9d0379cea6 consensus: use <cstdint> over <stdint.h> in amount.h (fanquake)
863e52fe63 consensus: make COIN & MAX_MONEY constexpr (fanquake)
d09071da5b [MOVEONLY] consensus: move amount.h into consensus (fanquake)

Pull request description:

  A first step (of a few) towards some source code reorganization, as well as making libbitcoinconsensus slightly more self contained.

  Related to #15732.

ACKs for top commit:
  MarcoFalke:
    concept ACK 9d0379cea6 🏝

Tree-SHA512: 97fc79262dcb8c00996852a288fee69ddf8398ae2c95700bba5b326f1f38ffcfaf8fa66e29d0cb446d9b3f4e608a96525fae0c2ad9cd531ad98ad2a4a687cd6a

src/util/moneystr.cpp

@@ -5,7 +5,7 @@
 
 #include <util/moneystr.h>
 
-#include <amount.h>
+#include <consensus/amount.h>
 #include <tinyformat.h>
 #include <util/strencodings.h>
 #include <util/string.h>

src/util/moneystr.h

@@ -9,8 +9,8 @@
 #ifndef BITCOIN_UTIL_MONEYSTR_H
 #define BITCOIN_UTIL_MONEYSTR_H
 
-#include <amount.h>
 #include <attributes.h>
+#include <consensus/amount.h>
 
 #include <optional>
 #include <string>