Add more Rust vendor image support.

This adds Rust vendor image support for all module types except
Rust prebuilts.

Bug: 184042776
Test: New Soong tests.
Test: Example cc_library vendor module can depend on rust_ffi_shared.
Test: Example rust_library vendor-only module compiles.

Change-Id: Iaa30ad51fdaedcbf14687da5472581f6af62ff59
diff --git a/rust/testing.go b/rust/testing.go
index 09c627f..f41d5a1 100644
--- a/rust/testing.go
+++ b/rust/testing.go
@@ -127,6 +127,7 @@
 			system_shared_libs: [],
 			apex_available: ["//apex_available:platform", "//apex_available:anyapex"],
 			min_sdk_version: "29",
+			vendor_available: true,
 		}
 		cc_library {
 			name: "libprotobuf-cpp-full",