* contracts: Implement refcounting for wasm code

* contracts: Charge rent for code storage

* contracts: Fix dispatchables erroneously refunding base costs

* Fixed typos in comments.

Co-authored-by: Andrew Jones <[email protected]>

* Remove awkward empty line

* Fix more typos in docs

* Fix typos in docs

Co-authored-by: Andrew Jones <[email protected]>

* Split up complicated expression

Co-authored-by: Andrew Jones <[email protected]>

* review: Remove unused return value

* Fix typos

Co-authored-by: Andrew Jones <[email protected]>

* review: Fix refcount being reset to one on re-instrumentation

* Document evictable_code parameter

* Make Executable::execute consume and store itself

* Added comments about stale values

* Disregard struct size in occupied_storage()

Co-authored-by: Andrew Jones <[email protected]>