aconfig: improve dump --format=debug output

Use Rust's {:#?} formatter for more readable output.

Bug: 279485059
Test: atest aconfig.test
Change-Id: I127f413e3d7aebfba96cad1dd58d9e261dd613a4
diff --git a/tools/aconfig/src/commands.rs b/tools/aconfig/src/commands.rs
index 22de331..c854b62 100644
--- a/tools/aconfig/src/commands.rs
+++ b/tools/aconfig/src/commands.rs
@@ -125,7 +125,7 @@
             DumpFormat::Debug => {
                 let mut lines = vec![];
                 for item in cache.iter() {
-                    lines.push(format!("{:?}\n", item));
+                    lines.push(format!("{:#?}\n", item));
                 }
                 output.append(&mut lines.concat().into());
             }