Simplify add cluster view (#2716)

- Only shows editor, and will save all text to file

- Reports some validation errors, but doesn't block the add cluster
  button

- Cleanup kube helpers to facilitate clearer FS interactions

Signed-off-by: Sebastian Malton <sebastian@malton.name>

src/renderer/components/cluster-settings/components/cluster-proxy-setting.tsx

@@ -58,7 +58,7 @@ export class ClusterProxySetting extends React.Component<Props> {
   render() {
     return (
       <>
-        <SubTitle title="HTTP Proxy" />
+        <SubTitle title="HTTP Proxy" id="http-proxy" />
         <Input
           theme="round-black"
           value={this.proxy}