test: parse the command line arguments in unit tests

Retrieve the command line arguments from boost and pass them to
`BasicTestingSetup` so that we gain extra flexibility of passing any
config options on the test command line, e.g.:

```
test_bitcoin -- -printtoconsole=1 -checkaddrman=5
```

src/qt/test/test_main.cpp

@@ -22,6 +22,7 @@
 #include <QApplication>
 #include <QObject>
 #include <QTest>
+#include <functional>
 
 #if defined(QT_STATICPLUGIN)
 #include <QtPlugin>
@@ -43,6 +44,8 @@ using node::NodeContext;
 
 const std::function<void(const std::string&)> G_TEST_LOG_FUN{};
 
+const std::function<std::vector<const char*>()> G_TEST_COMMAND_LINE_ARGUMENTS{};
+
 // This is all you need to run all the tests
 int main(int argc, char* argv[])
 {