CLI - Set default server to testnet

[dylanh724]

Description of Changes

testnet is quite stable now and makes onboarding (both the UX and docs) a significantly more-streamlined experience

• from "local"
• Suggested by @cloutiertyler

API and ABI breaking changes

(This is technically a breaking change? I'm not quite sure what label to apply)

Expected complexity level and risk

*How complicated do you think these changes are? Grade on a scale from 1 to 5,
2

⚠️ There may be some tooling that assumes local if they never explicitly set it to testnet.

Testing

Describe any testing you've done, and any testing you'd like your reviewers to do,
so that you're confident that all the changes work as expected!

• Try it in a new user env

[dylanh724]

Specific poke to @jdetter - heard you're working on CLI stuff now!👋

[jdetter]

We originally had the CLI pointing to testnet by default, I don't remember the exact reason why we changed it back to local. Changing it back to testnet has some implications but we could possibly get this into the next release. I'll talk to Tyler about it today.

[cloutiertyler]

We originally had the CLI pointing to testnet by default, I don't remember the exact reason why we changed it back to local. Changing it back to testnet has some implications but we could possibly get this into the next release. I'll talk to Tyler about it today.

The reason was that testnet was not stable and we were afraid that people would be trying to do the tutorial while Testnet was down. Now that it has been more stable, I think this change makes sense.

[jdetter]

LGTM

[jdetter]

I have to double check that the smoketests are working properly after this change

[jdetter]

We'll have to rework this PR after #1151 lands

[jdetter]

LGTM 👍