Settings: Migrate settings based on bundle

[martastain]

Story

Every client struggles with creating a new bundle and copying the settings for new addons we had many arguments against the automation but it seems it is something we need to address.

After a new bundle is created, users should be able to decide if they want to copy studio AND project level overrides.

Proposal

• You create a new bundle. Before submitting, a dialog would appear "Would you like to copy current production settings to a new staging bundle?"
• If they choose yes, that bundle would be also marked as staging and settings migration would be attempted (since it would be invoked from the bundles page, we don't have the option to display the copy dialog - it would just do the "best fit").
• It would copy both studio and project overrides (probably for active projects only)
• User could then ensure staging settings are correct and then use "push to production" (which would be updated to handle project overrides as well - there's already a WIP PR for that: Settings: copy project settings when promoting a bundle #311