Remove the beta update hooks at RC1, with 1.0.0-beta10 as the required stepping stone

Problem/Motivation

Betas have added one update hook per config change: display_builder_update_11101 to 11106 and display_builder_post_update_1 to _9. All of them only migrate beta data. From RC1, config schema and APIs are frozen, so these hooks are dead code for any site already past the betas.

Keeping them costs more than dead code:

• Each schema change can break an older hook that saves a profile. #3624051: Failed: InvalidArgumentException after update (drush updatedb) to 1.0.0-beta7: post update 3 saved profiles while state.revert still had its beta6 shape, and the update failed on every beta6 site.
• Post updates run in string order, so _10 runs before _2. That already happened: the two post updates numbered _10 and _11 in 1.0.x-dev sorted between _1 and _2, and ProfileUpgradePathTest went red. They were renamed after what they do, which is how every post update is named from now on.
• Helpers like ProfileIslandsUpdater::splitControlsIsland() and ::removeValueOnlyKeys() exist only for one beta hook.

Deleting the hooks without declaring them is not an option: a site jumping from an early beta to RC1 would skip them silently and keep invalid config.

Proposed resolution

Make 1.0.0-beta10 the required stepping stone. It ships every beta hook, including the #3624051: Failed: InvalidArgumentException after update (drush updatedb) to 1.0.0-beta7 fix, and ProfileUpgradePathTest runs the default profile of beta4 to beta7 through them.

At RC1:

• Delete display_builder_update_11101 to 11106 and declare hook_update_last_removed():
  

  function display_builder_update_last_removed(): int {
    return 11106;
  }
  

• Delete display_builder_post_update_1 to _9 and declare them in hook_removed_post_updates(), all mapped to 1.0.0-beta10, the release a site must install first:
  

  function display_builder_removed_post_updates(): array {
    return array_fill_keys([
      'display_builder_post_update_1',
      // ...
      'display_builder_post_update_9',
    ], '1.0.0-beta10');
  }
  

  Core then blocks update.php and drush updb on a site that skipped beta10, with a message naming it. Nothing is skipped silently.

• Keep the named post updates: they are the 1.x ones.
• Remove ProfileIslandsUpdater::splitControlsIsland() and ::removeValueOnlyKeys(). Keep ProfileIslandsUpdater itself: it is the tool for 1.x updates.
• Replace the beta fixtures of ProfileUpgradePathTest with the RC1 default profile, so the test guards every 1.x update the same way.

From RC1 on:

• Never reset update hooks again in 1.x.
• Name post updates after what they do, for example display_builder_post_update_add_scaffold_options(), not by number.
• Start new hook_update_N at 11200.
• Convert stored data the schema no longer accepts in a hook_update_N, which always runs before post updates, not in a post update.

Remaining tasks

• Tag 1.0.0-beta9 with the #3624051: Failed: InvalidArgumentException after update (drush updatedb) to 1.0.0-beta7 fix, then 1.0.0-beta10 as the last beta.
• Release notes for beta10 and RC1: update to beta10 and run drush updb before RC1.
• Implement the removal at RC1.
• Check on a beta7 site that drush updb on RC1 fails with the beta10 message, and passes after beta10.

User interface changes

None.

API changes

Removed: ProfileIslandsUpdater::splitControlsIsland(), ProfileIslandsUpdater::removeValueOnlyKeys().

Data model changes

None. Sites must be on 1.0.0-beta10 before updating to RC1.