Started implementation for private flags in rust (#7269)

Adds flag to the cpp to fix bad annotations in all the languages

Addresses comments to the PR, and fixes logic for leaking annotations

tests/private_annotation_test/object_generated.rs

@@ -0,0 +1,131 @@
+// automatically generated by the FlatBuffers compiler, do not modify
+extern crate alloc;
+extern crate flatbuffers;
+use alloc::boxed::Box;
+use alloc::string::{String, ToString};
+use alloc::vec::Vec;
+use core::mem;
+use core::cmp::Ordering;
+use self::flatbuffers::{EndianScalar, Follow};
+use super::*;
+// struct Object, aligned to 4
+#[repr(transparent)]
+#[derive(Clone, Copy, PartialEq)]
+pub(crate) struct Object(pub [u8; 4]);
+impl Default for Object { 
+  fn default() -> Self { 
+    Self([0; 4])
+  }
+}
+impl core::fmt::Debug for Object {
+  fn fmt(&self, f: &mut core::fmt::Formatter) -> core::fmt::Result {
+    f.debug_struct("Object")
+      .field("value", &self.value())
+      .finish()
+  }
+}
+
+impl flatbuffers::SimpleToVerifyInSlice for Object {}
+impl flatbuffers::SafeSliceAccess for Object {}
+impl<'a> flatbuffers::Follow<'a> for Object {
+  type Inner = &'a Object;
+  #[inline]
+  fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
+    <&'a Object>::follow(buf, loc)
+  }
+}
+impl<'a> flatbuffers::Follow<'a> for &'a Object {
+  type Inner = &'a Object;
+  #[inline]
+  fn follow(buf: &'a [u8], loc: usize) -> Self::Inner {
+    flatbuffers::follow_cast_ref::<Object>(buf, loc)
+  }
+}
+impl<'b> flatbuffers::Push for Object {
+    type Output = Object;
+    #[inline]
+    fn push(&self, dst: &mut [u8], _rest: &[u8]) {
+        let src = unsafe {
+            ::core::slice::from_raw_parts(self as *const Object as *const u8, Self::size())
+        };
+        dst.copy_from_slice(src);
+    }
+}
+impl<'b> flatbuffers::Push for &'b Object {
+    type Output = Object;
+
+    #[inline]
+    fn push(&self, dst: &mut [u8], _rest: &[u8]) {
+        let src = unsafe {
+            ::core::slice::from_raw_parts(*self as *const Object as *const u8, Self::size())
+        };
+        dst.copy_from_slice(src);
+    }
+}
+
+impl<'a> flatbuffers::Verifiable for Object {
+  #[inline]
+  fn run_verifier(
+    v: &mut flatbuffers::Verifier, pos: usize
+  ) -> Result<(), flatbuffers::InvalidFlatbuffer> {
+    use self::flatbuffers::Verifiable;
+    v.in_buffer::<Self>(pos)
+  }
+}
+
+impl<'a> Object {
+  #[allow(clippy::too_many_arguments)]
+  pub fn new(
+    value: i32,
+  ) -> Self {
+    let mut s = Self([0; 4]);
+    s.set_value(value);
+    s
+  }
+
+  pub const fn get_fully_qualified_name() -> &'static str {
+    "Object"
+  }
+
+  pub fn value(&self) -> i32 {
+    let mut mem = core::mem::MaybeUninit::<i32>::uninit();
+    unsafe {
+      core::ptr::copy_nonoverlapping(
+        self.0[0..].as_ptr(),
+        mem.as_mut_ptr() as *mut u8,
+        core::mem::size_of::<i32>(),
+      );
+      mem.assume_init()
+    }.from_little_endian()
+  }
+
+  pub fn set_value(&mut self, x: i32) {
+    let x_le = x.to_little_endian();
+    unsafe {
+      core::ptr::copy_nonoverlapping(
+        &x_le as *const i32 as *const u8,
+        self.0[0..].as_mut_ptr(),
+        core::mem::size_of::<i32>(),
+      );
+    }
+  }
+
+  pub fn unpack(&self) -> ObjectT {
+    ObjectT {
+      value: self.value(),
+    }
+  }
+}
+
+#[derive(Debug, Clone, PartialEq, Default)]
+pub(crate) struct ObjectT {
+  pub value: i32,
+}
+impl ObjectT {
+  pub fn pack(&self) -> Object {
+    Object::new(
+      self.value,
+    )
+  }
+}
+