Improve Template Maintainability

[XavierChanth]

Is your feature request related to a problem? Please describe.

Right now, the template bricks are not setup as individual dart/flutter projects which makes analysis and dependency maintenance challenging.

Describe the solution you'd like

• [ ] Spike brickhub for the package samples
• [x] Remodel demos and template bricks to be maintainable dart projects (i.e. move dependencies and other config from template.yaml to a pubspec.yaml) [Waiting to see what happens to mason for this one] #148

Describe alternatives you've considered N/A

Additional context N/A

[ksanty]

@XavierChanth should we move up to high priority for work on PR43?

[XavierChanth]

This can be bumped to a low.

[XavierChanth]

Closing this issue until mason and brickhub are stable, no work can be done until then.