Migrate away from structopt

Clap 3 supports derive natively, so we don't need structopt anymore
(since it was based on clap 2).

Besides, sort the arguments to make positional ones first.

Bug: 246385183
Test: atest AuthFsHostTest ComposHostTestCases MicrodroidTestCase
Change-Id: I75e25ffcb63bf717be8deb9720e0fdf78a0c7ccf
diff --git a/vm/Android.bp b/vm/Android.bp
index eac640e..7b016d4 100644
--- a/vm/Android.bp
+++ b/vm/Android.bp
@@ -12,6 +12,7 @@
         "android.system.virtualizationservice-rust",
         "libanyhow",
         "libbinder_rs",
+        "libclap",
         "libenv_logger",
         "liblibc",
         "liblog_rust",
@@ -19,7 +20,6 @@
         "librustutils",
         "libserde_json",
         "libserde",
-        "libstructopt",
         "libvmconfig",
         "libvmclient",
         "libzip",