What problem does this feature solve?

Continued from web-infra-dev/rspack#10290

What does the proposed API look like?

The main issue is that this will be a breaking change, so this should wait until the next major release. According to @chenjiahan the next breaking change will be Q3 2025 when we upgrade the minimum-supported Node version from v16. I propose we include the default browser target upgrade in that release too.