clippy cleanup #2

- remove needless return
- remove needless format!
- remove a few more needless clone()
- from_str_radix(_, 10) -> .parse()
- remove needless reference
- remove needless `mut`

Also manually replaced a match statement with map_err() because after
clippy was done with it, there was almost nothing left in the match
expression.

pageserver/src/waldecoder.rs

@@ -227,7 +227,7 @@ impl WalStreamDecoder {
         // FIXME: check that hdr.xlp_rem_len matches self.contlen
         //println!("next xlog page (xlp_rem_len: {})", hdr.xlp_rem_len);
 
-        return hdr;
+        hdr
     }
 
     #[allow(non_snake_case)]
@@ -239,7 +239,7 @@ impl WalStreamDecoder {
             xlp_xlog_blcksz: self.inputbuf.get_u32_le(),
         };
 
-        return hdr;
+        hdr
     }
 }
 
@@ -350,7 +350,7 @@ fn is_xlog_switch_record(rec: &Bytes) -> bool {
     buf.advance(2); // 2 bytes of padding
     let _xl_crc = buf.get_u32_le();
 
-    return xl_info == pg_constants::XLOG_SWITCH && xl_rmid == pg_constants::RM_XLOG_ID;
+    xl_info == pg_constants::XLOG_SWITCH && xl_rmid == pg_constants::RM_XLOG_ID
 }
 
 #[derive(Clone, Copy)]
@@ -651,6 +651,6 @@ pub fn decode_wal_record(rec: Bytes) -> DecodedWALRecord {
     DecodedWALRecord {
         record: rec,
         blocks,
-        main_data_offset: main_data_offset,
+        main_data_offset,
     }
 }