[#354] api/netmap: Return a slice of parameters directly

`IterateParameters` does a poor job:
- it doesn't encapsulate well, because it returns a pointer,
- it has a clunky interface, compared to range loop.

I have decided to return parameter slice and not `iter.Seq` for 2
reasons:
1. There already is `SetParameters`, so `NetworkConfig` struct is
   expected to be modified.
2. This iterator uses pointers, so even with this interface the slice
   can already be changed.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

api/netmap/types.go

@@ -577,6 +577,8 @@ type NetworkConfig struct {
 }
 
 // NumberOfParameters returns number of network parameters.
+//
+// Deprecated: use [NetworkConfig.Parameters] instead.
 func (x *NetworkConfig) NumberOfParameters() int {
 	if x != nil {
 		return len(x.ps)
@@ -585,10 +587,20 @@ func (x *NetworkConfig) NumberOfParameters() int {
 	return 0
 }
 
+// Parameters returns an iterator over network parameters.
+func (x *NetworkConfig) Parameters() []NetworkParameter {
+	if x != nil {
+		return x.ps
+	}
+	return nil
+}
+
 // IterateParameters iterates over network parameters.
 // Breaks iteration on f's true return.
 //
 // Handler must not be nil.
+//
+// Deprecated: use [NetworkConfig.Parameters] instead.
 func (x *NetworkConfig) IterateParameters(f func(*NetworkParameter) bool) {
 	if x != nil {
 		for i := range x.ps {