* [#3033] fix: sqlite3 drop/renameColumn() breaks with postProcessResponse
* When postProcessResponse is configured, and client.processResponse()
returns a Promise (e.g. for custom cases such as sqlite3 dropColumn()),
then that Promise is not awaited, but handed to postProcessResponse,
which might break is (e.g. with Objection's knexSnakeCaseMappers()).
* when reinserting data in the modified table, the rows are now being
handled with the "mapped" identifiers (instead of the unmapped)
* add tests, fix hasColumn
* add hasColumn tests for add mysql + snakeCaseMappers
* Improve tests and fix more cases related to processing
* Fix SQLite-specific tests
* MySQL is not case-sensitive, pg is
