Use C string literals not cstr!

Since Rust 1.77.0 the language has supported C string literals, so the
`cstr!` macro is no longer needed. Replace existing usages with the
equivalent literal.

See https://doc.rust-lang.org/reference/tokens.html#c-string-literals.

I believe that the two are equivalent:
- Escapes are handled the same way;
- Both allow arbitrary Unicode, which is mapped to UTF-8 (I don't
  think we made any use of this);
- Both treat any embedded NUL character as a compile time error.

This is of no significance whatsoever, but it does make the code a
tiny bit simpler. It should not change the compiled code at all, so
no flagging should be needed.

I'm not deleting the macro in this CL; I'll do a follow-up for that,
since there may be usages I can't see, and it has greater chance of
accidental conflict.

Test: TH
Change-Id: I4354b3b0a0c53fbec0c2d78b4182786e4e2d0ce8
diff --git a/android/virtmgr/src/aidl.rs b/android/virtmgr/src/aidl.rs
index c71b5c5..5ad7ee1 100644
--- a/android/virtmgr/src/aidl.rs
+++ b/android/virtmgr/src/aidl.rs
@@ -68,7 +68,6 @@
     self, wait_for_interface, Accessor, BinderFeatures, ConnectionInfo, ExceptionCode, Interface, ParcelFileDescriptor,
     SpIBinder, Status, StatusCode, Strong, IntoBinderResult,
 };
-use cstr::cstr;
 use glob::glob;
 use libc::{AF_VSOCK, sa_family_t, sockaddr_vm};
 use log::{debug, error, info, warn};
@@ -976,7 +975,7 @@
             "Passing vendor hashtree digest to pvmfw. This will be rejected if it doesn't \
                 match the trusted digest in the pvmfw config, causing the VM to fail to start."
         );
-        vec![(cstr!("vendor_hashtree_descriptor_root_digest"), vendor_hashtree_digest.as_slice())]
+        vec![(c"vendor_hashtree_descriptor_root_digest", vendor_hashtree_digest.as_slice())]
     } else {
         vec![]
     };
@@ -984,18 +983,18 @@
     let key_material;
     let mut untrusted_props = Vec::with_capacity(2);
     if cfg!(llpvm_changes) {
-        untrusted_props.push((cstr!("instance-id"), &instance_id[..]));
+        untrusted_props.push((c"instance-id", &instance_id[..]));
         let want_updatable = extract_want_updatable(config);
         if want_updatable && is_secretkeeper_supported() {
             // Let guest know that it can defer rollback protection to Secretkeeper by setting
             // an empty property in untrusted node in DT. This enables Updatable VMs.
-            untrusted_props.push((cstr!("defer-rollback-protection"), &[]));
+            untrusted_props.push((c"defer-rollback-protection", &[]));
             let sk: Strong<dyn ISecretkeeper> =
                 binder::wait_for_interface(SECRETKEEPER_IDENTIFIER)?;
             if sk.getInterfaceVersion()? >= 2 {
                 let PublicKey { keyMaterial } = sk.getSecretkeeperIdentity()?;
                 key_material = keyMaterial;
-                trusted_props.push((cstr!("secretkeeper_public_key"), key_material.as_slice()));
+                trusted_props.push((c"secretkeeper_public_key", key_material.as_slice()));
             }
         }
     }