exchanges: shift GetDefaultConfig wrapper function to exchange.go (#1472)

* Shift wrapper function GetDefaultConfig to exchange.Base method definition, to ensure set defaults doesn't get called twice and to reduce code

* rm alphapoint bootstrap method as is defined as exchange.Base method

* add tests

* glorious: make it a function and make it IBOTEXCHANGE

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Co-authored-by: shazbert <ryan.oharareid@thrasher.io>

cmd/config_builder/builder.go

@@ -36,7 +36,7 @@ func main() {
 	cfgs := make([]config.Exchange, 0, len(exchanges))
 	for x := range exchanges {
 		var cfg *config.Exchange
-		cfg, err = exchanges[x].GetDefaultConfig(context.Background())
+		cfg, err = exchange.GetDefaultConfig(context.Background(), exchanges[x])
 		if err != nil {
 			log.Printf("Failed to get exchanges default config. Err: %s", err)
 			continue