Median by Position (#533)

* use median price instead of the highest sustained

* add test for lexicographically reversing a byte slice

* fix pr comments

* fix CI fail

* fix dex tests

* Use a fuzz-tested list of prices

* Working median algorithm based on position + lints

---------

Co-authored-by: akildemir <aeg_asd@hotmail.com>

Cargo.lock

@@ -7487,6 +7487,7 @@ dependencies = [
  "frame-support",
  "frame-system",
  "parity-scale-codec",
+ "rand_core",
  "scale-info",
  "serai-coins-pallet",
  "serai-primitives",
@@ -7687,10 +7688,12 @@ dependencies = [
  "borsh",
  "frame-support",
  "parity-scale-codec",
+ "rand_core",
  "scale-info",
  "serde",
  "sp-application-crypto",
  "sp-core",
+ "sp-io",
  "sp-runtime",
  "zeroize",
 ]