Field blocks are only exposed for bundles that have Layout Builder enabled

Prior to #3043330: Reduce the number of field blocks created for entities (possibly to zero) every field on every bundle on every entity type were exposed as field block plugins by layout_builder's FieldBlockDeriver and ExtraFieldBlockDeriver.

A new feature flag module has been added to control this behavior layout_builder_expose_all_field_blocks.

When this module is installed, the previous behavior is retained. The module will be installed by an update hook by default.

When this module not installed, fields are only exposed as blocks if at least one bundle using the field has layout builder enabled. This is the default state for new installations.

Leaving this module installed can significantly affect the performance of medium to large sites due to the number of Field Block plugins that will be created. It is recommended to turn it off if possible.

While it is recommended to uninstall it, please note that this may remove blocks that are already being used in existing site configurations.

For example, if you have Layout Builder enabled on a Node bundle (Content type), and that bundle's display is using field blocks for the User entity (e.g the Author's name), but Layout Builder is not enabled for the User bundle, then that field block would no longer exist after disabling this setting.