New command cargoLogin to login in all cargo registries

[qsantos]

It seems to work locally. Hopefully, it will also work in the CI.

[daladim]

Notes after a call: we should make sure this MR

• starts the MITM proxy (which is still required, can be disabled later)
• configures cargo to use this proxy
• configures cargo to be aware it is authenticated to a registry (otherwise we would hit a no token found for 'whatever-registry-here' error, even if kraken is using the proxy, as it looks kraken does not even attempt a request when it does not know the token)

[qsantos]

@daladim

Notes after a call: we should make sure this MR

* starts the MITM proxy (which is still required, can be disabled later)

* configures cargo to use this proxy

* configures cargo to be aware it is authenticated to a registry (otherwise we would hit a `no token found for 'whatever-registry-here'` error, even if kraken is using the proxy, as it looks kraken does not even attempt a request when it does not know the token)

Regarding the first two points, this MR does not touch CargoAuthProxyTask, is that enough?

For the last point, this is what #140 did, by adding cargo:token as a dummy global-credential-providers to convince Cargo to still attempt the request. This MR only adds more global-credential-providers, so it should still work.

[NiklasRosenstein]

I've only tested this marginally -- we really need some end-to-end tests that include a sparse and private registry. @Colin1860 recently added a test with https://github.com/d-e-s-o/cargo-http-registry but it's (1) not sparse and (2) accepts and credentials. I'm gonna go ahead with merging this anyway to unblock us integrating it into our internal extension module.