Summary

Initializes future flags. Rspack learned the technique for future flag from remix team.
Future flagging is fundamentally the same as other terms you may heard of like feature-gates, feature-flags.

Essentially, in Rspack, when it comes to adopting a deprecation or a newly added feature that differs from
the behavior of the previous version, a new future flag is added.

For example:

module.exports = {
  experiments: {
    rspackFuture: {
       disableTransformByDefault: true, // opt-in new deprecations
       newResolver: true
    }
  }
}

When adopting a new breaking behavior in Rspack, three steps are included:

1. In the current minor version, a breaking change is added with a new future flag. However,
   for the default behavior, this flag is off. You can adopt this feature by switching the flag.
   At the same time, a deprecation message with regard to the breaking will also be added.
2. In the next minor, the flag will be turned on by default. This is a breaking change.
   At this stage, you can still switch to the old implementation. This leaves people some time
   for adopting the new behavior later. For people who turned off the flag (which is enabled in this version),
   a deprecation message will be used as a heads-up.
3. In the minor version after that, the flag and its deprecation message will be completely removed.

In summary, developers have time of less than two releases to adopt to the new behavior.
This strategy is subject to change when it hits to our first major version.

Test Plan

Not necessary for now.