Issue #2030637 by yched, Mile23, daffie, Alumei, tidrif, chertzog, Berdir, swentel, ofry: Expand FieldConfig/BaseFieldOverride/FieldConfigBase with methods

Issue #2437785 by amateescu: FieldConfigStorageBase::mapToStorageRecord() calls the wrong field type method

Issue #2030633 by hussainweb, Mile23, carsonevans, czigor, Berdir, fernando_calsa, Geijutsuka, amitgoyal, Jānis Bebrītis, undertext: Expand FieldStorageConfig with methods

Issue #2395395 by alexpott, effulgentsia, Gábor Hojtsy: TestBase lacks a config method to be used consistently in tests

Issue #2377115 by mglaman: Replace all instances of entity_load('field_config') and entity_load_multiple('field_config') with static method calls

Issue #2312093 by alexpott, yched, andypost, swentel | xjm: Rename FieldInstanceConfig to FieldConfig.