implement BoundedEncodedLen (#8720)

* implement BoundedEncodedLen

* update header

* update imports

* use impl_for_tuples instead of a custom macro

* remove redundant where clause

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

* impl for Compact<T>

* impl BoundedEncodedLen for BoundedVec (#8727)

* impl BoundedEncodedLen for bool

* explicitly implement BoundedEncodedLen for each Compact form

Turns out that u16 doesn't play nicely with the pattern; those values
take two extra bytes, where all other cases take one. :(

* rename BoundedEncodedLen -> MaxEncodedLen

* add tests of compact encoded length

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>