feat(client): papi API (portfolioMargin) (#1436)

* feat(client): init papi API (portfolioMargin)

* more papi methods

* more sync methods

* fix encoding

* remove version override

* add async methods

* simplify test

* add ping test

* add more sync endpoints

* add more methods

* rest of trading endpoints

* add papi async endpoints

* update some methods names

* add id tests

* typo

* feat(AsyncClient): https_proxy support

* remove hardcoded url

* read https_proxy inside create

* update readme