Revert "Issue #1923406 by stefan.r, yannickoo: Use ASCII character set on alphanumeric fields so we can index all 255 characters"

This reverts commit ac4e35ce.

Issue #1923406 by stefan.r, yannickoo: Use ASCII character set on alphanumeric fields so we can index all 255 characters

Issue #2232477 by plach, yched, tstoeckler, amateescu: Fatal when adding new fields with NOT NULL constraints in a base table that contains existing entities

Issue #2313757 by Berdir, Wim Leers, dawehner: Remove text_processing option from text fields, expose existing string field types as plain text in UI.

Issue #2226197 by fago, jessebeach: Introduce FieldStorageDefinitionInterface in the Entity Field API.

Issue #2136197 by andypost, jessebeach, swentel, longwave, Berdir: Move field/instance/widget/formatter settings out of annotation / plugin definition.

Issue #2152825 by plopesc, swentel, Berdir: Rename FieldItemBase::getFieldSetting[s]() to getSetting[s]().

Issue #2058257 by effulgentsia: Fix ConfigFieldItemInterface's method signatures to typehint interfaces instead of classes.

Issue #1969728 by yched, effulgentsia, swentel, fago, plach: Implement Field API 'field types' as TypedData Plugins.