drush updb fails with "the 'media_delete_action' plugin does not exist" after 8.4.6 > 8.5.1 update
This is how we were able to solve this problem:

Temporarily install drupal/media_entity_actions:

composer require drupal/media_entity_actions:^1.0
drush en media_entity_actions


Run the database update:

drush updb


This time it will work:

system module :
  Change plugin IDs of actions.
  Clear caches due to schema changes in core.entity.schema.yml.

views module :
  Update dependencies for moved bulk field plugin.
  Add additional settings to the entity link field and convert node_path usage  to entity_link.
  Add placeholder settings to string or numeric filters.
  Fix cache max age for table displays.
  Include views data table provider in views dependencies.

Do you wish to run all pending updates? (y/n): y
Post updating system                                                                                                       [ok]
Post updating system                                                                                                       [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Post updating views                                                                                                        [ok]
Cache rebuild complete.                                                                                                    [ok]
Finished performing updates.                                                                                               [ok]


Then the module can be uninstalled safely:

drush pm-uninstall media_entity_actions
composer remove drupal/media_entity_actions