DEV: Add pry-byebug and optionally require pry behind a ENV var for better spec debugging (#9984)

We removed pry-nav a while back because it is not up to date with pry but it is super useful. Luckily pry-byebug is here to save us all from Satan's power.

To get this to work you need to add the following to your $HOME/.pryrc file.

```
if defined?(PryByebug)
  Pry.commands.alias_command 'c', 'continue'
  Pry.commands.alias_command 's', 'step'
  Pry.commands.alias_command 'n', 'next'
  Pry.commands.alias_command 'f', 'finish'
end

Pry::Commands.command /^$/, "repeat last command" do
  pry_instance.run_command Pry.history.to_a.last
end
```

The require-ing of pry, pry-rails, and pry-byebug in specs is controlled by the IMPROVED_SPEC_DEBUGGING flag (disabled by default).

Gemfile

@@ -112,6 +112,7 @@ gem 'oj'
 gem 'pg'
 gem 'mini_sql'
 gem 'pry-rails', require: false
+gem 'pry-byebug', require: false
 gem 'r2', require: false
 gem 'rake'