Upgrade from futures-preview to futures 0.3.1, and remove futures 0.1 where currently possible (#4083)

* Migrate node and node-template

* Migrate srml

* Simple changes

* Add async-std for interval

* Fix test-runtime warning

* Small changes

* move futures01 in core/rpc to dev-deps

* Change wasm CI builds

* Switch to async-std 1.0.1

* Remove async-std dep of network

* Add modified lockfile

* Fix node cli browser build

* Remove authority-discovery async-std dep

* Add Send + Sync to interval dyn stream

* Fisr migrated version of weight to paint

* Bump

* Minor nits

* Some review fixes.

* Line width

* Revert spec bump

* Fix build

* Update lock file

* Update palette/executive/src/lib.rs

Co-Authored-By: Bastian Köcher <[email protected]>

* Update palette/membership/src/lib.rs

Co-Authored-By: Bastian Köcher <[email protected]>

* /paint to /palette

* rename paint to palette

* rename the modules in palette to be pallets

* update Structure.adoc

* bump impl

* fix CI directory

* Update docs/Structure.adoc

Co-Authored-By: Benjamin Kampmann <[email protected]>