fix: improve install and add error messages for pre-release drivers

[amoeba]

Updates dbc install and dbc add to provide command suggestions for pre-release drivers.

For example: Currently, if I try to dbc install a driver that only has a pre-release available, I get an error message that isn't that helpful,

$ dbc install fakedriver
Error: driver `fakedriver` not found (but prerelease versions filtered out)

This PR updates the error so it recommends the user try --pre:

$ dbc install fakedriver
Error: driver `fakedriver` not found (but prerelease versions filtered out); try: dbc install --pre fakedriver

This error only happens if the driver only has pre-release versions and the user doesn't specify --pre. It's not a perfect heuristic but I think it'll work well.

[ianmcook]

Thanks for doing this!

[amoeba]

Updated PR to include coverage for dbc add as well.

[ianmcook]

What about the case when only pre-release versions are available on the registry, and you already have a pre-release version installed?

For example, what should happen when you do:

dbc install --pre singlestore
dbc install singlestore

[zeroshade]

Bah, i missed @ianmcook's question.

@amoeba can you still answer the question there and determine if we need a follow-up PR?

[amoeba]

I don't think that behavior is changed by this PR so I'll create a new issue.

[amoeba]

#340