Avoid setting fixed app name in console prompt

[st0012]

Motivation / Background

IRB allows changing its prompt's name during the session, like:

irb(main):001> conf.irb_name = "foo"
=> "foo"
foo(main):002> 

But because I previously set the app name as part of the prompt, instead of via the irb_name config, such change can't happen in a Rails console:

Loading development environment (Rails 7.2.0.alpha)
test-app(dev)> conf.irb_name = "foo"
=> "foo"
test-app(dev)> 

This can be problematic as tools/features can rely on the name change to indicate state change (example).

Detail

Instead of setting app name as a fixed value in prompt, I replaced it with %N, which IRB uses to display the irb_name attribute. And then we can set assign the app name to IRB.conf[:IRB_NAME] (default is "irb").

Additional information

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[flavorjones]

Looks good! Can you squash these commits?

[rafaelfranca]

Test seems to be failing now because of this change

[st0012]

Sorry for causing the failure. It's likely caused by the latest IRB release and was not caught here because the branch hadn't bumped its version yet.