[AVRO-3710] [C++] Permit DataFile use without stream ownership

[Gerrit0]

What is the purpose of the change

As requested by AVRO-3710, this makes it possible to create DataFile reader and writer instances which do not take exclusive ownership of their underlying stream. This makes it more convenient to use data files without effectively being forced to write to a file.

This also fixes an issue with the build format and cppcheck steps which were broken with #3042

Verifying this change

(Please pick one of the following options)

This change added a test demonstrating the use of DataFile reader/writer constructors which do not take exclusive ownership of the pointer.

Documentation

• Does this pull request introduce a new feature? yes
• If yes, how is the feature documented? Included in doc comments for data file classes