feat(iota-types)!: update to MoveStruct with contents checked

[Thoralf-M]

This PR follows up on the MoveObjectType / MoveStruct migration in
iota-rust-sdk. The SDK's MoveStruct (re-exported in iota-types as
MoveObject) has been hardened: its fields are now private, construction
goes through a fallible MoveStruct::new constructor, and replacing the
contents goes through a fallible set_contents setter — both of which
validate that contents is at least ObjectId::LENGTH (32) bytes, since
every Move object must carry its ObjectId as the leading bytes of its
BCS payload. This PR adapts the iota-types and execution call sites to
the new API.

Description of change

• iota-types::object (MoveObjectExt) no longer reaches into
  MoveObject fields directly. All self.object_type / self.version
  / self.contents accesses are replaced with the corresponding
  object_type() / version() / contents() getters; mutations go
  through set_version() and the fallible set_contents() (returning
  MoveStructContentsError, mapped to ExecutionError::invariant_violation
  on the production path).
• MoveObjectExt::set_coin_value_unchecked and
  set_clock_timestamp_ms_unchecked no longer mutate the contents buffer
  in place via Vec::splice — they now copy the buffer
  (self.contents().to_vec()), patch the trailing 8 bytes, and pass it
  back through set_contents(...).unwrap() (the length is unchanged, so
  the length check cannot fail).
• All MoveObject { object_type, version, contents } struct-literal
  constructions in Object::*_for_testing helpers and in
  MoveObjectExt::new_from_execution_with_limit are replaced with
  MoveObject::new(...). Test helpers .unwrap() the result; the
  execution path maps the error to ExecutionError::invariant_violation.
• The associated helper MoveObject::id_opt(&bytes) (which extracted an
  ObjectId from the leading bytes of a raw payload) was removed in the
  SDK now that the same invariant is upheld by the constructor. The two
  call sites in iota-adapter::programmable_transactions::context are
  updated to call ObjectID::from_bytes(&bytes[..ObjectID::LENGTH])
  directly, with the missing-bytes case turning into an
  ExecutionError::invariant_violation.
• iota-open-rpc::examples had a MoveObject::new_from_execution_with_limit
  call that built an example object with an empty contents: Vec::new()
  and an empty MoveStructLayout. Empty contents now fail the new
  length check, so the example is updated to construct a 32-byte payload
  via UID::new(parent_object_id).to_bcs_bytes() and a matching layout
  with a single id: UID field. Generated openrpc.json snapshots are
  regenerated to reflect the new example payload.

Release Notes

• Protocol:
• Nodes (Validators and Full nodes):
• Indexer:
• JSON-RPC:
• GraphQL:
• CLI:
• Rust SDK: MoveStruct (re-exported as iota-types::object::MoveObject)
  now has private fields. Construction must go through
  MoveStruct::new(object_type, version, contents) and content updates
  through set_contents(...); both are fallible and reject contents
  shorter than ObjectId::LENGTH (32 bytes), since every Move object
  must carry its ObjectId as the leading bytes. The associated helper
  MoveObject::id_opt(&bytes) has been removed — call
  ObjectID::from_bytes(&bytes[..ObjectID::LENGTH]) directly. Direct
  field access (.object_type, .version, .contents) is replaced by
  the equivalent getter methods. Wire formats (BCS and JSON) are
  unchanged.
• gRPC: