Rework Annotations UI + annotation class refactor

[cleaaum]

This PR re works the UI for the annotation class and annotation tools. It also refactors the way the annotation classes are defined in memory. They are implemented using an OOP approach in which each class has its own set of properties such as as visibility, annotations, color, label etc. These can now easily be processed using MATCH callbacks.

[github-actions[bot]]

Staging application has been deployed and is available at: https://dash5-services.plotly.host/ml-exchange-staging Production app name: ml-exchange Current branch name: issue94-annotationsUI Commit: 47df3eef7c115387f328b4ea1198853e02867ed9

[hannahker]

Closes #75 and #94

[hannahker]

This looks amazing! I've spent time clicking around the UI and can't seem to be able to break anything. This is in the stage of fixing typos and nit-picky UI tweaks.

• Can we update the styling on this disclaimer text so that it's more aligned with the rest of the UI? (ie. update the font and add some padding)

• Can we reduce the amount of white space between the "Annotation tools" header and the "Drawing toolbar" text?
• Can we expand the width of the drawing toolbar so that it matches the full width of each class button?
• We should add some padding to the right of the garbage icon so that it doesn't come right up to the edge of the button when it's highlighted.

Otherwise, this should be good to merge once I finish up with the work to update the annotations data handling.