Add env variable to disable experimental.browserDebugInfoInTerminal
Add __NEXT_DISABLE_BROWSER_DEBUG_INFO_IN_TERMINAL env variable that can
be set to 'true' to disable the browserDebugInfoInTerminal feature.
This follows the same pattern as other experimental feature env
variables like __NEXT_EXPERIMENTAL_DEBUG_CHANNEL,
__NEXT_EXPERIMENTAL_STRICT_ROUTE_TYPES, etc.