Request review from @rtibblesbot and community to community contributor PRs

[rtibbles]

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Overview

Automatically request review from @rtibblesbot and community on community contributor pull requests

Complexity: Low
Target branch: main

Context

We currently do this for dependabot PRs.

The Change

Use our existing techniques for deciding if a contributor is a community contributor (which gates whether we send automated messages on the PR) to request review from @rtibblesbot - similar to how we do for dependabot PRs.
Apply the community review label also.
Update how we message about bot and community review on PRs - they no longer need to be gated separately, and can be messaged in the first comment on the PR as it is now default behaviour.

Out of Scope

Autoclosing unsolicited PRs - for now the bot will review all PRs.

Acceptance Criteria

• Bot review is auto requested
• Follow up bot review message is removed
• Community review label is auto applied
• Follow up community review message is removed
• Language for community and bot review is incorporated into the default community contributor message

AI usage

None

[rtibbles]

Folded back into parent issue.