[C++] Implement a mock "high latency" filesystem

[asfimport]

Some of our tools don't perform well out of the box for filesystems with high latency reads, like cloud blob stores. In such cases, it may be better to use buffered reads with a larger read ahead window. Having a mock filesystem to introduce latency into reads will help with testing / developing APIs for this

Reporter: Wes McKinney / @wesm
Assignee: Antoine Pitrou / @pitrou

PRs and other links:

• GitHub Pull Request #5439

_{Note: This issue was originally created as ARROW-3777. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
First thing would be to create slow input and output stream wrappers (though I'm not sure it makes sense for output streams: writes are normally issued in the background).

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 5439
#5439