v146.8.0

Merge upstream denoland/rusty_v8 into openworkers/rusty-v8

Brings in simdutf support, crdtp/deno_inspector, PlatformImpl task ownership.

Resolved conflicts:
- Cargo.toml: kept openworkers-v8 name/description, took upstream version 146.8.0
- ci.yml: kept our features string system (none/ptrcomp/sandbox), removed upstream
  simdutf-only builds, simdutf now always enabled in all builds
- Cargo.lock: regenerated from scratch