Revert "Copy AppBuilder Base class verbatim from FAB to Airflow (with attribution) (#19322)" (#19661)
Revert "Copy AppBuilder Base class verbatim from FAB to Airflow (with attribution) (#19322)" (#19661)

This reverts commit 37a12e9c278209d7e8ea914012a31a91a6c6ccff.
danielvdende/incubator-airflow,apache/airflow,nathanielvarona/airflow,lyft/incubator-airflow,apache/airflow,nathanielvarona/airflow,Acehaidrey/incubator-airflow,lyft/incubator-airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,bolkedebruin/airflow,lyft/incubator-airflow,mistercrunch/airflow,bolkedebruin/airflow,Acehaidrey/incubator-airflow,Acehaidrey/incubator-airflow,bolkedebruin/airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,bolkedebruin/airflow,nathanielvarona/airflow,danielvdende/incubator-airflow,nathanielvarona/airflow,cfei18/incubator-airflow,mistercrunch/airflow,apache/airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,Acehaidrey/incubator-airflow,apache/airflow,apache/airflow,lyft/incubator-airflow,danielvdende/incubator-airflow,cfei18/incubator-airflow,danielvdende/incubator-airflow,apache/airflow,cfei18/incubator-airflow,nathanielvarona/airflow,mistercrunch/airflow,nathanielvarona/airflow,mistercrunch/airflow