Updating the commit modal to save to backpack and support new flow

[hannahbergam]

This PR updates the backpack/commit modal. It utilizes the built in button settings for disabled/abled colors. The final modal differs slightly from the Figma spec, so here are the logic rules:

1. The Commit button is "Commit" if there are no backpack files checked, "Commit & Save" otherwise
2. The Commit button is greyed out until there are commit notes
3. The compilation status only displays if there are backpack files checked

Because the default buttons site-wide use gray as a default color instead of a light gold, we switched to match the settings for the green buttons (therefore removing the use of orange/gold at all).

The Cancel button closes the dialog exactly the way the corner "X" does.

The different states of the button colors and text are shown below.

Files compile, no commit notes yet or files checked for save:

Files compile, no commit notes, files checked for save:

Files compile, commit notes, no files checked for save:

Files compile, commit notes, files checked for save:

Links

• spec: https://www.figma.com/file/fZo4fcZmDUioOCaz04Gza4/Javalab-Design-Spec?node-id=405%3A1545
• jira ticket: https://codedotorg.atlassian.net/browse/CSA-551

Testing story

Deployment strategy

Follow-up work

Privacy

Security

Caching

PR Checklist:

• Tests provide adequate coverage
• Privacy and Security impacts have been assessed
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Pull Request is labeled appropriately
• Follow-up work items (including potential tech debt) are tracked and linked

[maureensturgeon]

LGTM! I definitely defer to the CSA team though

[molly-moen]

Looks good! Just a couple nits