rpc: Move ValueFromAmount to core_write

This is necessary because core_write has to write amounts in
TxToUniv, and mistakingly uses FormatMoney for that
(which is only for debugging).

We don't move AmountFromValue at the same time, as
this is more challenging due to the RPCError depencency
there.

src/rpc/server.cpp

@@ -123,16 +123,6 @@ CAmount AmountFromValue(const UniValue& value)
     return amount;
 }
 
-UniValue ValueFromAmount(const CAmount& amount)
-{
-    bool sign = amount < 0;
-    int64_t n_abs = (sign ? -amount : amount);
-    int64_t quotient = n_abs / COIN;
-    int64_t remainder = n_abs % COIN;
-    return UniValue(UniValue::VNUM,
-            strprintf("%s%d.%08d", sign ? "-" : "", quotient, remainder));
-}
-
 uint256 ParseHashV(const UniValue& v, std::string strName)
 {
     std::string strHex;