feat: Ability to run multiple instances of shorebird cli

[maheshj01]

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Description While a shorebird command is already running it would be nice to be able to run another instance of shorebird parallely

mahesh@MacBook-Pro-10 life_in_dots % shorebird doctor
Waiting for another flutter command to release the startup lock...

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Requirements

• [ ] Checklist of requirements to be fulfilled

Additional Context

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