printflags: introduce device tool to print feature flags

Metadata about all feature flags used on device are located in
/<partition>/etc/aconfig_flags.pb. Add a new tool, printflags, to read
and pretty-print these files.

printflags is only intended for debugging purposes.

Bug: 301547297
Test: adb shell printflags
Change-Id: I0a3277fecfc8a60eea0aa6bf362a25a311360b71
diff --git a/tools/aconfig/printflags/Android.bp b/tools/aconfig/printflags/Android.bp
new file mode 100644
index 0000000..5d73d96
--- /dev/null
+++ b/tools/aconfig/printflags/Android.bp
@@ -0,0 +1,16 @@
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+rust_binary {
+    name: "printflags",
+    edition: "2021",
+    clippy_lints: "android",
+    lints: "android",
+    srcs: ["src/main.rs"],
+    rustlibs: [
+        "libaconfig_protos",
+        "libanyhow",
+        "libprotobuf",
+    ],
+}