Move Codelabs from blocklycodelabs.dev to DevSite

[NeilFraser]

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Component

Codelabs

Problem

The codelabs have a lot of moving parts which aren't needed. The Google-internal Gerrit repo, the dedicated App Engine instance, the domain name. Each of these are unnecessary dependencies which create long-term maintenance issues.

Request

Move the published code labs to a tab on DevSite (so they are part of the existing docs). Replace the content in App Engine with redirects.

Keep Claat.

Alternatives considered

There was some debate as to whether the content sources of the codelabs should be moved from blockly-samples to our documentation repo, or left alone.

Additional context

There was such a lack of awareness of the App Engine instance that we didn't recognise that it was running Python 2.7 until a week before it would be shutdown. Likewise, at least one team member can't push to Gerrit, and there's no understanding of why. This particular issue is low priority, but in general we should strive to have fewer systems.

As discussed on the 23.01.2024 team meeting.