[C++] Support Flight RPC among diffent endian platforms

[asfimport]

This PR is derived from discussion in ARROW-8790. The current implementation of the Flight RPC exchanges messages using a native endlian format. It does not allow us to exchange data though Flight RPC among different endian machines (e.g. x86_64 <-> s390x).

There is a field to show an endianness at https://github.com/apache/arrow/blob/master/format/Schema.fbs#L343-L346, which is added by ARROW-245.

Reporter: Kazuaki Ishizaki / @kiszk
Assignee: Kazuaki Ishizaki / @kiszk

PRs and other links:

• GitHub Pull Request #41
• GitHub Pull Request #58
• GitHub Pull Request #7507

_{Note: This issue was originally created as ARROW-8797. Please see the migration documentation for further details.}

[asfimport]

Kazuaki Ishizaki / @kiszk:
@pitrou According to your comment, current FlightRPC transfers data in native endlian. In my opinion, we may have two opinions to exchange data between different endian platforms.

1. Exchange data using native endian. If the receiver detects the message endian is different from the machine-native endian, the receiver converts endian.
2. The FlightRPC always use the specific endian regardless of endian of sender or receiver.

Is there any comment?

[asfimport]

Antoine Pitrou / @pitrou:
This is a general issue with our IPC implementation. The IPC format specifies the data endianness in the Schema structure:
https://github.com/apache/arrow/blob/master/format/Schema.fbs#L343-L346

However, this is currently ignored in the implemenation, so it will have to be fixed.

[asfimport]

Kazuaki Ishizaki / @kiszk:
Sure, IPC should exchange data using the data endianness in the schema. Then, a reader has to take care of the field.

First, we may have to create test cases.

[asfimport]

Kazuaki Ishizaki / @kiszk:
#7507 is trying to create test cases.

[asfimport]

Antoine Pitrou / @pitrou:
Issue resolved by pull request 7507
#7507