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

{
    
    
    
    
    TestParse("", true, 0);
    TestParse(" ", false, 0);
    TestParse("0", false, 0);
    TestParse("0 ", false, 0);
    TestParse(" 0", false, 0);
    TestParse("+0", false, 0);
    TestParse("-0", false, 0);
    TestParse("5", true, 5);
    TestParse("5 ", true, 5);
    TestParse(" 5", true, 5);
    TestParse("+5", true, 5);
    TestParse("-5", true, -5);
    TestParse("0 5", false, 0);
    TestParse("5 0", true, 5);
    TestParse("050", true, 50);
    TestParse("0.", false, 0);
    TestParse("5.", true, 5);
    TestParse("0.0", false, 0);
    TestParse("0.5", false, 0);
    TestParse("5.0", true, 5);