Massive restructure of plugin API

plug-api/plugos-syscall/shell.ts

@@ -0,0 +1,8 @@
+import { syscall } from "./syscall.ts";
+
+export function run(
+  cmd: string,
+  args: string[],
+): Promise<{ stdout: string; stderr: string }> {
+  return syscall("shell.run", cmd, args);
+}