Issue #3033925 by AaronBauman: Expose standalone pull mechanism, analogous to standalone push

config/schema/salesforce.schema.yml

...force_mapping/config/schema/salesforce_mapping.schema.yml

modules/salesforce_mapping/src/Entity/SalesforceMapping.php

...esforce_mapping/src/Entity/SalesforceMappingInterface.php

modules/salesforce_mapping/src/SalesforceMappingStorage.php

...rce_mapping_ui/src/Form/SalesforceMappingFormCrudBase.php

modules/salesforce_pull/salesforce_pull.install

modules/salesforce_pull/salesforce_pull.module

modules/salesforce_pull/salesforce_pull.routing.yml

modules/salesforce_pull/src/Controller/PullController.php

modules/salesforce_pull/src/QueueHandler.php

modules/salesforce_pull/tests/src/Unit/QueueHandlerTest.php

src/Form/SettingsForm.php

src/SelectQueryResult.php