Pull out `storage-plus`, `multitest` and `utils` into a separate repo

[uint]

These have become tooling that is used everywhere. They're not specific to this repo anymore.

• Create new repos: cw-utils, cw-storage-plus, cw-multi-test
• Transfer issues from this repo to the new ones
• Make sure cw-awesome lists where all these things live
• Remove the crates from this repo
• Update documentation
• Update scripts
• Update CI

[ethanfrey]

This is a good idea to separate the contracts/specs and the util packages.

Besides multi-test and maybe storage-plus, everything else can easily be 1.0 in the repo.
Not sure if we should pull out all the contracts actually... and leave cw-plus to these core packages.

Let's do it an get to a 1.0. Throw ideas on naming here

[ueco-jb]

cw-storage
cw-multitest
it's not taken, right?

[uint]

This is a go. On it!

[uint]

This is just waiting for CosmWasm/awesome-cosmwasm#18 to be merged. Then we can link to cw-awesome from the top-lever README here and we're done!

[uint]

All done!