Update CONTRIBUTING.md MIGRATION.md (#2762)

CONTRIBUTING.md

@@ -24,7 +24,7 @@ Once the package is installed, simply run `pre-commit install` to enable the hoo
 Before making your pull requests, try to see if your code follows these rules.
 
 - Wherever possible, use `Cow<'static, str>` instead of String.
-- `PhantomData` should have the smallest set of types needed.
+- `PhantomData` should have the smallest set of types needed. Try not adding `PhantomData` to your struct unless it is really necessary. Also even when you really need `PhantomData`, try to keep the types `T` used in `PhantomData` as smallest as possible 
 - Wherever possible, trait implementations with lifetime specifiers should use '_ lifetime elision.
 - Complex constructors should be replaced with `typed_builder`, or write code in the builder pattern for yourself.
 - Remove generic restrictions at the definitions (e.g., we do not need to specify that types impl `Serialize`, `Deserialize`, or `Debug` anymore at the struct definitions). Therefore, try avoiding code like this unless the contraint is really necessary.

MIGRATION.md

@@ -5,6 +5,8 @@
 - Removed `with_observers` from `Executor` trait.
 - `MmapShMemProvider::new_shmem_persistent` has been removed in favour of `MmapShMem::persist`. You probably want to do something like this: `let shmem = MmapShMemProvider::new()?.new_shmem(size)?.persist()?;`
 
-# 0.14.1 -> 0.14.2
+# 0.14.1 -> 0.15.0
 - `MmapShMem::new` and `MmapShMemProvider::new_shmem_with_id` now take `AsRef<Path>` instead of a byte array for the filename/id.
-- The closure passed to a `DumpToDiskStage` now provides the `Testcase` instead of just the `Input`.
+- The closure passed to a `DumpToDiskStage` now provides the `Testcase` instead of just the `Input`.
+- `StatsStage` is deleted, and it is superceded by `AflStatsStage`
+- 

libafl/Cargo.toml

@@ -28,7 +28,6 @@ rustc-args = ["--cfg", "docsrs"]
 
 [features]
 default = [
-  "introspection",
   "std",
   "derive",
   "llmp_compression",