feat(shorebird_cli): check for available upgrade after command run

[bryanoltman]

Description

At the end of every command run (except for upgrade), check whether there is a newer stable version of shorebird available than what is running. If there is, inform the user and tell them to run shorebird upgrade.

Fixes #1910

Type of Change

• ✨ New feature (non-breaking change which adds functionality)
• 🛠️ Bug fix (non-breaking change which fixes an issue)
• ❌ Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 Code refactor
• ✅ Build configuration change
• 📝 Documentation
• 🗑️ Chore
• 🧪 Tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (6fb9f2a) to head (ec86fc4).

Additional details and impacted files

@@            Coverage Diff            @@
##              main     #2184   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          184       184           
  Lines         5726      5741   +15     
=========================================
+ Hits          5726      5741   +15     

Flag	Coverage Δ
shorebird_cli	100.00% <100.00%> (ø)

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