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

[HuaHuaY]

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
• Allow inferring the number of columns based on the longest row read by the BlockParser
• Allow the CSV Reader to accept multi-character delimiters

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++