This is part of the effort to streamline package updates and reduce unnecessary manual toil.

PR Highlights:

• [existing] Test all major in isolation via independent PRs
• [new] Consolidate configuration for major updates in one place (simplifies currently separate config)
• [new] Group minor, patch, pin, and digest updates in the same category (separating them proved to be too noisy)
• [existing] Further group updates to devDependencies into subpackage, build-system, validator, core, linting, babel, esbuild, and ampproject
• [existing] Also group updates to dependencies into ampproject (published by @ampproject) and core (all others)
• [new] Enable renovate updates for core (not published by @ampproject) dependencies (see Upgrade Preact to 10.5.13 #30043 (comment))
• [new] Explicitly enable automerge for devDependencies, and explicitly disable for dependencies
• [new] Enable assignAutomerge for all groups that have automerge set to true (to be used by renovate-approve)
• [new] Make sure all upgrade PRs are tagged with appropriate working-group label(s)

Reference: https://docs.renovatebot.com/configuration-options

Partial fix for #33959