Branch-specific environment variable values from the Netlify UI, CLI, or API

The Netlify UI has been updated to allow teams to set different values for specific branches on environment variables. This change allows developers to manage branch-specific configurations and preview site updates with specific API tokens without needing netlify.toml configuration or build plugins. The update also includes support for the Netlify CLI and API, enabling teams to scope environment variables and set values for specific deploy contexts using new flags and endpoints. With this change, shared environment variables will apply to all Sites in a Team, and developers can now locally emulate builds from specific branches using the `netlify dev` command.