Unsound types: SharedMemoryReader & SharedMemoryManager

[JEnoch]

Starting from 1.58 Clippy reported this issue:

error: this implementation is unsound, as some fields in `SharedMemoryReader` are `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:211:1
    |
211 | unsafe impl Send for SharedMemoryReader {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::non-send-fields-in-send-ty` implied by `-D warnings`
note: the type of field `segments` is `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:208:5
    |
208 |     segments: HashMap<String, Shmem>,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: use a thread-safe type that implements `Send`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#non_send_fields_in_send_ty
error: this implementation is unsound, as some fields in `SharedMemoryManager` are `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:300:1
    |
300 | unsafe impl Send for SharedMemoryManager {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
note: the type of field `own_segment` is `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:294:5
    |
294 |     own_segment: Shmem,
    |     ^^^^^^^^^^^^^^^^^^
    = help: use a thread-safe type that implements `Send`
note: the type of field `free_list` is `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:295:5
    |
295 |     free_list: BinaryHeap<Chunk>,
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: use a thread-safe type that implements `Send`
note: the type of field `busy_list` is `!Send`
   --> zenoh/src/net/protocol/io/shm.rs:296:5
    |
296 |     busy_list: Vec<Chunk>,
    |     ^^^^^^^^^^^^^^^^^^^^^
    = help: use a thread-safe type that implements `Send`
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#non_send_fields_in_send_ty
error: could not compile `zenoh` due to 2 previous errors

The current workaround is to allow this warning.
But we need a more definitive solution.

[Mallets]

The default behaviour in clippy has been reverted because of high number of false positive: rust-lang/rust-clippy#8045.

Need to check if the workaround is still needed or it can be removed.