Make libbinder_rs vendor available.

Add vendor_available: true to libbinder_rs and dependencies.
Also remove set_requesting_sid conditionally if building the vendor
variant.

Test: Vendor components can compile and link against libbinder_rs.
Bug: 198197213
Change-Id: I9ad9ed226e76c16bff7d3feb201fd9fef20ad934
diff --git a/libs/binder/rust/Android.bp b/libs/binder/rust/Android.bp
index d323022..4561d6e 100644
--- a/libs/binder/rust/Android.bp
+++ b/libs/binder/rust/Android.bp
@@ -20,6 +20,7 @@
         "libdowncast_rs",
     ],
     host_supported: true,
+    vendor_available: true,
     target: {
         darwin: {
             enabled: false,
@@ -64,6 +65,7 @@
         "libbinder_ndk",
     ],
     host_supported: true,
+    vendor_available: true,
     target: {
         darwin: {
             enabled: false,
@@ -105,6 +107,7 @@
         "libbinder_ndk",
     ],
     host_supported: true,
+    vendor_available: true,
 
     // Currently necessary for host builds
     // TODO(b/31559095): bionic on host should define this