[C++] Provided more options in CSV reader's ParseOptions and ReadOptions #50966

Describe the enhancement requested

I hope that the following new features to be added to the CSV Reader:

• Allow null padding for rows with fewer columns [C++] Allow CSV reader to pad rows with missing trailing fields #50925
• Allow ignoring extra columns in rows with more columns [C++] Allow CSV reader to ignore extra columns in rows with more columns #50967
• Allow inferring the number of columns based on the longest row read by the BlockParser
• Allow the CSV Reader to accept multi-character delimiters [C++] Allow the CSV Reader to accept multi-character delimiters #51275

I have already implemented these features on my local environment, and I plan to submit the PRs within a week.

cc @pitrou

Component(s)

C++