Fix EZP-23408: use correct scope 'image' for images in legacy IO handler
EZP-23368: Migrated "border" filter.
EZP-23368: Added filter/noise filter loader
EZP-23368: Added comment on why "flatten" filter has been discarded
EZP-23368: Added info about resize filter
EZP-23368: Added colorspace/gray filter loader
EZP-23368: Added filter/swirl filter and loader.
EZP-23368: Ensure filters and loaders are private services
EZP-23368: Added BC doc
Merge pull request #1010 from ezsystems/impl_EZP-23368_legacyImageFiltersMigration

Fix EZP-23368: Migrate image filters leftovers
Merge pull request #1012 from joaoinacio/EZP-23408_dfs_image_scope

Fix EZP-23408: use correct scope 'image' for images in legacy IO handler
Improvement EZP-22191: Change Criterion\LanguageCode to match alwaysAvailable content by default
Improvement EZP-22191: New \$useAlwaysAvailable argument for ContentService methods with language filtering

The bahavour is not enabled by default in this commit as this is meant for backports.
BC break when changing the default is that any code expecting to get exception when
not a specific translation exists will break if content is always avaiable and main
language is something else then what code is asking for.
Improvement EZP-22191: Change $useAlwaysAvailable arguments in ContentService to true by default
Improvement EZP-22191: Change SearchService to pass languages & useAlwaysAvailable $fieldFilters to ContentService