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
3452ee2bb0