Revert "rustc-1.66.1 Build 9561314"

Revert submission 2421642-rust-update-prebuilts-1.66.1

Reason for revert: Missing riscv support and out of date base64 crate causing brekages

Reverted changes: /q/submissionid:2421642-rust-update-prebuilts-1.66.1

Change-Id: I6c0d6c3539e766012570e4542f529706fe49928c
diff --git a/rust/config/global.go b/rust/config/global.go
index 2b224f5..50ac1f7 100644
--- a/rust/config/global.go
+++ b/rust/config/global.go
@@ -24,7 +24,7 @@
 var pctx = android.NewPackageContext("android/soong/rust/config")
 
 var (
-	RustDefaultVersion = "1.66.1"
+	RustDefaultVersion = "1.65.0.p1"
 	RustDefaultBase    = "prebuilts/rust/"
 	DefaultEdition     = "2021"
 	Stdlibs            = []string{
@@ -51,6 +51,9 @@
 		// Use v0 mangling to distinguish from C++ symbols
 		"-C symbol-mangling-version=v0",
 		"--color always",
+		// TODO (b/267698452): Temporary workaround until the "no unstable
+		// features" policy is enforced.
+		"-A stable-features",
 	}
 
 	deviceGlobalRustFlags = []string{