Drop inheritable caps and caps bounding set before executing payload

This change basically does the following things:

* Add rust_bindgen for the libcap.
* Add libcap_rust wrapping the bindgen and providing
  drop_inhertiable_caps and drop_bounding_set APIs;
* Call the libcap_rust APIs before execve'ing into the payload binary.
  This is done using the CommandExt::pre_exec function.

Additionally this change adds basic tests for libcap_rust library and
the e2e test to verify that binary running payload have zero
capabilities.

Bug: 243633980
Test: atest libcap_rust.test
Test: atest MicrodroidTestApp
Test: adb shell /apex/com.android.virt/bin/vm run-microdroid
Test: enter microdroid shell & check microdroid_launcher has empty caps
Change-Id: Ibfb45ec912df0ad0a1db62b24c22fbe5a61ff5f3
diff --git a/tests/testapk/Android.bp b/tests/testapk/Android.bp
index edb4759..e3c9961 100644
--- a/tests/testapk/Android.bp
+++ b/tests/testapk/Android.bp
@@ -40,6 +40,7 @@
     header_libs: ["vm_payload_restricted_headers"],
     shared_libs: [
         "libbinder_ndk",
+        "libcap",
         "MicrodroidTestNativeLibSub",
         "libvm_payload#current",
     ],