Regex parser should have the option to 'skip' some number of header rows like the CSV parser can

This would be super useful for ingesting data that has some form of a header such as what is seen in https://github.com/apache/incubator-druid/issues/8555.

Start by comparing the regex parser's ingestion path with the existing CSV parser support for skipping header rows. Define the desired option and verify that regex ingestion skips the requested number of rows while preserving the remaining records; the issue names no files or tests, so repository exploration is required.

Written by the indexing model from the issue text.