Add and Refactor CapnProto Input/Output Format

Why it matters

This feature enhances ClickHouse's support for the Cap'n Proto serialization format by enabling both reading (input) and writing (output) capabilities. It facilitates efficient data interchange with systems using Cap'n Proto, improving data serialization performance and compatibility.

How to use it

To use the CapnProto format, specify FORMAT CapnProto in your SELECT or INSERT statements for output or input respectively. For example:

SELECT * FROM table FORMAT CapnProto;

or

INSERT INTO table FORMAT CapnProto