[apkverify] Use ensure!() instead of bail!() in apk verification

This cl replaces the usage of `if (false) bail!` with ensure! in
apk verification to make the code more concise.

Test: libapkverify.integration_test
Bug: 246254355
Change-Id: If6e4673141ed463f8fd4ded61a993bb8afc1543a
diff --git a/libs/apkverify/src/bytes_ext.rs b/libs/apkverify/src/bytes_ext.rs
index 22a3085..8fb36ee 100644
--- a/libs/apkverify/src/bytes_ext.rs
+++ b/libs/apkverify/src/bytes_ext.rs
@@ -16,7 +16,7 @@
 
 //! Provides extension methods Bytes::read<T>(), which calls back ReadFromBytes::read_from_byte()
 
-use anyhow::{bail, Result};
+use anyhow::{ensure, Result};
 use bytes::{Buf, Bytes};
 use std::ops::Deref;
 
@@ -79,20 +79,18 @@
 }
 
 fn read_length_prefixed_slice(buf: &mut Bytes) -> Result<Bytes> {
-    if buf.remaining() < 4 {
-        bail!(
-            "Remaining buffer too short to contain length of length-prefixed field. Remaining: {}",
-            buf.remaining()
-        );
-    }
+    ensure!(
+        buf.remaining() >= 4,
+        "Remaining buffer too short to contain length of length-prefixed field. Remaining: {}",
+        buf.remaining()
+    );
     let len = buf.get_u32_le() as usize;
-    if len > buf.remaining() {
-        bail!(
-            "length-prefixed field longer than remaining buffer. Field length: {}, remaining: {}",
-            len,
-            buf.remaining()
-        );
-    }
+    ensure!(
+        buf.remaining() >= len,
+        "length-prefixed field longer than remaining buffer. Field length: {}, remaining: {}",
+        len,
+        buf.remaining()
+    );
     Ok(buf.split_to(len))
 }