Undici 8

[mcollina]

@nodejs/undici I'm going to ship v8 next week to be included in Node 26. If there is anything left you want to be part of that release, now it's the time.

Currently landed PR:

1. feat!: enable h2 by default #4828 – feat!: enable h2 by default
2. fix: preserve request statusText and update h2 dispatch tests #4830 – fix: preserve request statusText and update h2 dispatch tests
3. fix: isolate global dispatcher v2 and add Dispatcher1Wrapper bridge #4827 – fix: isolate global dispatcher v2 and add Dispatcher1Wrapper bridge
4. Remove legacy handler wrappers #4786 – Remove legacy handler wrappers