Implement IRB Customizations With .irbrc

[Hamms]

Rather than in dashboard code. The primary reason to avoid updating console.rb to conform to Zeitwerk's expectations, but the secondary reason is to avoid adding a file to lib/ which has side effects on being included. This code is not something we ever want to invoke as an actual code path, so we shouldn't treat it as such.

Links

• For historical context, see this blog post which recommends our original implementation: https://josh.fail/2015/customizing-the-rails-console/
• For more-recent context, see this one which recommends our new implementation: https://nts.strzibny.name/improving-irb-with-custom-irbrc/
• Add environment to the dashboard-console prompt #21748 (original PR)

Testing story

Tested locally:

[~/code-dot-org (implement-irb-customization-as-dotfile)]$ bin/dashboard-console
Running via Spring preloader in process 76862
Loading development environment (Rails 6.0.4.1)
irb: warn: can't alias context from irb_context.
[development] dashboard >

[~/code-dot-org (implement-irb-customization-as-dotfile)]$ cd dashboard/
[~/code-dot-org/dashboard (implement-irb-customization-as-dotfile)]$ ../bin/dashboard-console
Running via Spring preloader in process 76928
Loading development environment (Rails 6.0.4.1)
irb: warn: can't alias context from irb_context.
[development] dashboard >

PR Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[cat5inthecradle]

I don't fully understand how rails console works, but this PR makes sense otherwise.