`FormatMoney(CAmount n)` is not being properly defined for `n = std::numeric_limits<CAmount>::min()`. This is due to an invalid integer negation: the negation of `-9223372036854775808` cannot be represented in type `CAmount` (which has a max value of `9223372036854775807`):

https://github.com/bitcoin/bitcoin/blob/54f812d9d29893c690ae06b84aaeab128186aa36/src/util/moneystr.cpp#L12-L31

FWIW `FormatMoney(-9223372036854775808)` returns `--92233720368.-54775808` when compiled with UBSan (LLVM/Clang, `-fsanitize=undefined`).

Context: https://github.com/bitcoin/bitcoin/pull/20383#discussion_r523250890

It would be nice if `FormatMoney(CAmount n)` was properly defined for all `CAmount n` :)

These are the "expectations of least surprise":

```
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::max()), "92233720368.54775807");       //  9223372036854775807
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::max() - 1), "92233720368.54775806");   //  9223372036854775806
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::max() - 2), "92233720368.54775805");   //  9223372036854775805
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::max() - 3), "92233720368.54775804");   //  9223372036854775804
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::min() + 3), "-92233720368.54775805");  // -9223372036854775805
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::min() + 2), "-92233720368.54775806");  // -9223372036854775806
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::min() + 1), "-92233720368.54775807");  // -9223372036854775807
BOOST_CHECK_EQUAL(FormatMoney(std::numeric_limits<CAmount>::min()), "-92233720368.54775808");      // -9223372036854775808
```

These assertions are _guaranteed_ to hold for all cases above _except_ for the last one.
{
    using M = ArgsManager;
    CheckValue(M::ALLOW_ANY, nullptr, Expect{{}}.DefaultString().DefaultInt().DefaultBool().List({}));
    CheckValue(M::ALLOW_ANY, "-novalue", Expect{false}.String("0").Int(0).Bool(false).List({}));
    CheckValue(M::ALLOW_ANY, "-novalue=", Expect{false}.String("0").Int(0).Bool(false).List({}));
    CheckValue(M::ALLOW_ANY, "-novalue=0", Expect{true}.String("1").Int(1).Bool(true).List({"1"}));
    CheckValue(M::ALLOW_ANY, "-novalue=1", Expect{false}.String("0").Int(0).Bool(false).List({}));
    CheckValue(M::ALLOW_ANY, "-novalue=2", Expect{false}.String("0").Int(0).Bool(false).List({}));
    CheckValue(M::ALLOW_ANY, "-novalue=abc", Expect{true}.String("1").Int(1).Bool(true).List({"1"}));
    CheckValue(M::ALLOW_ANY, "-value", Expect{""}.String("").Int(0).Bool(true).List({""}));
    CheckValue(M::ALLOW_ANY, "-value=", Expect{""}.String("").Int(0).Bool(true).List({""}));
    CheckValue(M::ALLOW_ANY, "-value=0", Expect{"0"}.String("0").Int(0).Bool(false).List({"0"}));
    CheckValue(M::ALLOW_ANY, "-value=1", Expect{"1"}.String("1").Int(1).Bool(true).List({"1"}));
    CheckValue(M::ALLOW_ANY, "-value=2", Expect{"2"}.String("2").Int(2).Bool(true).List({"2"}));
    CheckValue(M::ALLOW_ANY, "-value=abc", Expect{"abc"}.String("abc").Int(0).Bool(false).List({"abc"}));
}
BOOST_AUTO_TEST_CASE(util_ParseParameters)
{