values smaller than 0.001 sat/B can't be represented by CFeeRate, but they are not rejected.

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.0009

error code: -6
error message:
Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)
```

```
./src/bitcoin-cli -named sendtoaddress address=bcrt1qwkmhqum095zau5rf2velq55cq938vrd7uw8m4r amount=1.23 fee_rate=0.000000000009

error code: -3
error message:
Invalid amount

BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_test_no_reg, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_EQUAL(test_args.GetChainName(), "test");
    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_both, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_THROW(test_args.GetChainName(), std::runtime_error);
    
    
    test_args.SelectConfigNetwork("test");
    BOOST_CHECK(test_args.ParseParameters(0, (char**)argv_testnet, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_EQUAL(test_args.GetChainName(), "test");
    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_testnet, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_EQUAL(test_args.GetChainName(), "test");
    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_regtest, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_THROW(test_args.GetChainName(), std::runtime_error);
    BOOST_CHECK(test_args.ParseParameters(2, (char**)argv_test_no_reg, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_EQUAL(test_args.GetChainName(), "test");
    BOOST_CHECK(test_args.ParseParameters(3, (char**)argv_both, error));
    test_args.ReadConfigString(testnetconf);
    BOOST_CHECK_THROW(test_args.GetChainName(), std::runtime_error);
}
struct ArgsMergeTestingSetup : public BasicTestingSetup {
    
    
    static constexpr int MAX_ACTIONS = 3;
    enum Action { NONE, SET, NEGATE, SECTION_SET, SECTION_NEGATE };