accounts/abi: Prevent recalculation of internal fields (#20895)

* accounts/abi: prevent recalculation of ID, Sig and String

* accounts/abi: fixed unpacking of no values

* accounts/abi: multiple fixes to arguments

* accounts/abi: refactored methodName and eventName

This commit moves the complicated logic of how we assign method names
and event names if they already exist into their own functions for
better readability.

* accounts/abi: prevent recalculation of internal

In this commit, I changed the way we calculate the string
representations, sig representations and the id's of methods. Before
that these fields would be recalculated everytime someone called .Sig()
.String() or .ID() on a method or an event.

Additionally this commit fixes issue #20856 as we assign names to inputs
with no name (input with name "" becomes "arg0")

* accounts/abi: added unnamed event params test

* accounts/abi: fixed rebasing errors in method sig

* accounts/abi: fixed rebasing errors in method sig

* accounts/abi: addressed comments

* accounts/abi: added FunctionType enumeration

* accounts/abi/bind: added test for unnamed arguments

* accounts/abi: improved readability in NewMethod, nitpicks

* accounts/abi: method/eventName -> overloadedMethodName

accounts/abi/bind/bind.go

@@ -639,9 +639,9 @@ func formatMethod(method abi.Method, structs map[string]*tmplStruct) string {
 		state = state + " "
 	}
 	identity := fmt.Sprintf("function %v", method.RawName)
-	if method.IsFallback {
+	if method.Type == abi.Fallback {
 		identity = "fallback"
-	} else if method.IsReceive {
+	} else if method.Type == abi.Receive {
 		identity = "receive"
 	}
 	return fmt.Sprintf("%s(%v) %sreturns(%v)", identity, strings.Join(inputs, ", "), state, strings.Join(outputs, ", "))