Consider renaming `cargo dev setup intellij` command to `cargo dev setup rustrover`

[reddevilmidzy]

JetBrains has transitioned from the IntelliJ Rust plugin to RustRover as their dedicated Rust IDE. We've already updated the documentation in #15448, but the command name still references "intellij".

Current Situation

• The command cargo dev setup intellij still works and is functional
• Documentation has been updated to reference RustRover instead of IntelliJ Rust
• The command name creates a slight disconnect with the updated documentation

Question for Maintainers

I'm considering two approaches for updating the command name and would like to hear your thoughts:

1: Add new command + deprecate old (Recommended)

• Add cargo dev setup rustrover as the new primary command
• Mark cargo dev setup intellij as deprecated but keep it functional
• This maintains backward compatibility while providing a more accurate command name

2: Direct rename

• Simply rename cargo dev setup intellij to cargo dev setup rustrover
• This is cleaner but breaks existing scripts/workflows that might depend on the old command name

Which approach do you prefer?

@rustbot label C-question