Issue #2075095 by yched, amateescu: Widget / Formatter methods signatures needlessly complex.

...etime/Plugin/field/formatter/DatetimeDefaultFormatter.php

...atetime/Plugin/field/formatter/DatetimePlainFormatter.php

...l/datetime/Plugin/field/widget/DatetimeDatelistWidget.php

...al/datetime/Plugin/field/widget/DatetimeDefaultWidget.php

...b/Drupal/email/Plugin/field/formatter/MailToFormatter.php

...b/Drupal/email/Plugin/field/widget/EmailDefaultWidget.php

...Plugin/field/formatter/EntityReferenceEntityFormatter.php

...e/Plugin/field/formatter/EntityReferenceFormatterBase.php

...nce/Plugin/field/formatter/EntityReferenceIdFormatter.php

.../Plugin/field/formatter/EntityReferenceLabelFormatter.php

...tity_reference/Plugin/field/widget/AutocompleteWidget.php

..._reference/Plugin/field/widget/AutocompleteWidgetBase.php

core/modules/field/field.api.php

core/modules/field/field.attach.inc

core/modules/field/field.module

core/modules/field/field.multilingual.inc

...ld/lib/Drupal/field/Plugin/Type/FieldType/ConfigField.php

.../lib/Drupal/field/Plugin/Type/Formatter/FormatterBase.php

...Drupal/field/Plugin/Type/Formatter/FormatterInterface.php

.../field/lib/Drupal/field/Plugin/Type/Widget/WidgetBase.php