[C++] FileSystem::OpenInput{File,Stream} should accept a MemoryPool

[asfimport]

#8533 (comment)

Currently buffers read from files opened by a FileSystem will always be allocated from the default memory pool. This is contrary to the Arrow convention of allowing control over memory allocation.

Reporter: Ben Kietzman / @bkietz
Assignee: Antoine Pitrou / @pitrou

PRs and other links:

• GitHub Pull Request #9474

_{Note: This issue was originally created as ARROW-10420. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
Would it be better to pass it in OpenInput(File|Stream) or when constructing the filesystem instance?

[asfimport]

Antoine Pitrou / @pitrou:
Also cc @wesm for advice.

[asfimport]

Wes McKinney / @wesm:
If you are going to do this, I suggest creating an IOContext object or similar so that it's easier to add other IO-related options later 

[asfimport]

Antoine Pitrou / @pitrou:
That doesn't answer the question I asked above :-)

[asfimport]

Wes McKinney / @wesm:
It seems like at the FileSystem level would be less intrusive

[asfimport]

Ben Kietzman / @bkietz:
Issue resolved by pull request 9474
#9474