fix: merge iterator

would return wrong data during ping-pong read

Author: marvin-j97

Cargo.toml

@@ -2,7 +2,7 @@
 name = "lsm-tree"
 description = "A K.I.S.S. implementation of log-structured merge trees (LSM-trees/LSMTs)"
 license = "MIT OR Apache-2.0"
-version = "0.6.3"
+version = "0.6.4"
 edition = "2021"
 rust-version = "1.74.0"
 readme = "README.md"
@@ -26,11 +26,11 @@ byteorder = "1.5.0"
 chrono = "0.4.38"
 crc32fast = "1.4.0"
 crossbeam-skiplist = "0.1.3"
+double-ended-peekable = "0.1.0"
 fs_extra = "1.3.0"
 guardian = "1.1.0"
 log = "0.4.21"
 lz4_flex = "0.11.3"
-min-max-heap = "1.3.0"
 path-absolutize = "3.1.1"
 quick_cache = { version = "0.5.1", default-features = false, features = [] }
 rand = "0.8.5"