[Feature Request] List available targets from bundle config

[GMorrisXBL]

Feature Request

Summary

Add a databricks bundle targets (or databricks bundle list-targets) subcommand that prints the targets defined in the current bundle's databricks.yml.

Motivation

Bundles often define multiple targets (e.g. dev, feature, staging, prod). Currently there is no way to
introspect which targets are available without manually opening databricks.yml. This is a friction point for:

• CI/CD pipelines that want to enumerate valid --target values dynamically
• Developers onboarding to a new bundle who want to discover available targets
• Tooling/scripts that wrap databricks bundle deploy

Proposed Behaviour

$ databricks bundle targets                                                                                           
NAME       DEFAULT  WORKSPACE                                                                                         
dev        true     https://dbc-xxxxxxxx-1234.cloud.databricks.com                                                    
feature    false    https://dbc-yyyyyyyy-1234.cloud.databricks.com                                                    
prod       false    https://adb-123456789.azuredatabricks.net                                                         

JSON output via -o json should also be supported, consistent with existing commands.

[GMorrisXBL]

Happy to do this if it is agreed on 😄