feat: replace InterfaceFilter with ForwardRequirements, add WildcardListener, complete alpha.20 bump

- Replace DynInterfaceFilter with ForwardRequirements for per-IP forward
  precision with source-subnet iptables filtering for private forwards
- Add WildcardListener (binds [::]:port) to replace the per-gateway
  NetworkInterfaceListener/SelfContainedNetworkInterfaceListener/
  UpgradableListener infrastructure
- Update forward-port script with src_subnet and excluded_src env vars
- Remove unused filter types and listener infrastructure from gateway.rs
- Add availablePorts migration (IdPool -> BTreeMap<u16, bool>) to alpha.20
- Complete version bump to 0.4.0-alpha.20 in SDK and web

sdk/package/lib/StartSdk.ts

@@ -67,7 +67,7 @@ import {
 import { getOwnServiceInterfaces } from '../../base/lib/util/getServiceInterfaces'
 import { Volumes, createVolumes } from './util/Volume'
 
-export const OSVersion = testTypeVersion('0.4.0-alpha.19')
+export const OSVersion = testTypeVersion('0.4.0-alpha.20')
 
 // prettier-ignore
 type AnyNeverCond<T extends any[], Then, Else> =