[Tracking]: Merging Addon Functionality into Core

[valentinpalkovic]

This milestone aims to merge multiple standalone Storybook addons into the core framework, reducing package fragmentation and improving performance. The goal is to simplify maintenance, improve user experience, and streamline configuration for users by making these addons part of the core manager.

Items:

1. Merge @storybook/addon-controls into Core

• Remove @storybook/addon-controls package and integrate functionality into the core manager
• Move implementation from addon-controls into storybook/core​
• Move ArgsTable component to core for compatibility with @storybook/addon-docs.​
• Update documentation and migration notes​
• Write an automigration script

2. Merge @storybook/addon-toolbars into Core

• Remove @storybook/addon-toolbars and integrate its behavior into core
• Move implementation and ensure API consistency​
• Update documentation and migration notes​
• Write an automigration script

3. Merge @storybook/addon-viewport into Core

• Remove @storybook/addon-viewport and integrate its behavior into core
• Update migration documentation​
• Write an automigration script

4. Merge Toolbar-Based Addons (measure, outline, backgrounds)

• Remove @storybook/addon-measure, @storybook/addon-outline, and @storybook/addon-backgrounds, integrating them into core
• Update documentation and migration notes​
• Write automigrations where applicable

5. Merge @storybook/addon-highlight into storybook/internal/manager-api

• Remove @storybook/addon-highlight package and integrate its functionality into storybook/internal/manager-api
• Move implementation into the internal manager API​
• Update documentation and migration guides​

6. Remove @storybook/addon-essentials Package

• Remove @storybook/addon-essentials package as it becomes obsolete
• Remove explicit handling of the package in the codebase​
• Ensure @storybook/addon-docs is installed during init when documentation is selected
• Update migration documentation and guides​
• Write an automigration script to remove the dependency

7. Remove Deprecated @storybook/addon-mdx-gfm

• Remove @storybook/addon-mdx-gfm package
• Remove package references from the monorepo
• Update existing automigrations that reference this package