Ensure data size of identity pallet is bounded (#9168)

* Ensure data size of identity pallet is bounded

* Fix unit tests for identity pallet

* Move identity pallet custom types into its own module

* Make use of NoBound family traits

* Fix identity pallet benchmarks

* Enumerate type imports

* Properly convert to BoundedVec in benchmarks

* Re-export types

* Use BoundedVec when storing sub identities

* Add generate_storage_info

* Manually implement MaxEncodedLen on select types

* Use ConstU32 instead of parameter_type

* Leverage DefaultNoBound and add some comments

* Use max_encoded_len() instead of hardcoded constant

* Use MaxEncodedLen in parity-scal-codec

* Add get_mut method for WeakBoundedVec

* Use expect on an infallible operation

* Rewrite as for loop