Draft: Eliminate 2-phase kernel boot in the installer #3574200

Merge InstallerServiceProvider and NormalInstallerServiceProvider into a single provider that checks $install_state['base_system_verified'] to select early-phase (fallback config, memory keyvalue, null routing) or post-install (database-backed) services.

Introduce InstallerFallbackConfigStorage which writes to DatabaseStorage with lazy table creation and falls back to InstallStorage for reads. This allows config writes during the early phase without rebooting the kernel.

Remove the explicit kernel shutdown/rebuildContainer/boot cycle from drupal_install_system(). Instead, set base_system_verified=TRUE and let ModuleInstaller::install(['system']) trigger the container rebuild which picks up the flag and switches to full services.

Deprecate NormalInstallerServiceProvider (removed in drupal:13.0.0).

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

Closes #3574200