feat(configuration): set default channel to stable

[kwonoj]

• closes Warn nightly users if rls is missing in the active toolchain #217

Feel freely close if this isn't desired direction - as it's small changes I took stab directly via PR.
This PR changes default channel to stable, prevents rustup update nightly doesn't have rls-preview breaks extension behavior.

[Xanewok]

Thanks for the PR!

I agree that the current situation with rls not being available every nightly isn't ideal, but rather than setting it by default to stable, it'd be good to use user's default toolchain instead (as described in #179).
There was work for this in #180 but it's currently not continued anymore - is it something that you would be willing to work on?

[kwonoj]

yeah, let me peek if I can make changes,

[Xanewok]

@kwonoj ah my bad, I'm sorry. I went ahead and gave it a shot in the meantime at #220. However, if you're still willing to work on this or the nightly availability and rustup update issues in general, there is still work to do. 🙂

One notable improvement would be to detect if the rls-preview component is available and possibly detect what earliest nightly build has it. With this information we could warn the user that it's not available and suggest switching the channel to the earliest in which the rls is available.

Another good thing would be to start including tests for the extension itself, since it seems we stripped them some time ago. First possible good test would be to see if the rustup show parsing in the #220 works as expected.

[kwonoj]

closing as PR's now obsolete. I'll try another chance to contribute.