Implement a `CountedStorageMap` (#9125)

* initial impl

* expose in pallet_prelude

* temp test

* Apply suggestions from code review

Co-authored-by: Peter Goodspeed-Niklaus <[email protected]>
Co-authored-by: Xiliang Chen <[email protected]>

* implement with macro help.

* test for macro generation

* add iterable functions, some test and fixes

* fix merge

* doc

* Update frame/support/src/storage/types/counted_map.rs

Co-authored-by: Zeke Mostov <[email protected]>

* fix merge

* fmt

* fix spelling

* improve on removal

* fix partial storage info

* fmt

* add license

* suggested renames

* fix typo

* fix test

* fmt

* fix ui tests

* clearer doc

* better doc

* add metadata test

Co-authored-by: Shawn Tabrizi <[email protected]>
Co-authored-by: Peter Goodspeed-Niklaus <[email protected]>
Co-authored-by: Xiliang Chen <[email protected]>
Co-authored-by: Zeke Mostov <[email protected]>