Add string/json output string mc pipe

[fennm]

This commit adds a string message and json output to mc pipe. The implementation is heavily inspired by the one in mc cp, just adapted to the different semantics of pipe.

Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

The mc pipe command doesn't currently do anything with the --json global flag, and this PR implements that. Feel free to suggest any changes to make this more conformant with project style or other requirements.

Motivation and Context

Comparing the number of bytes copied with the number of bytes expected is do a simple end-to-end check that an upload went as expected.

How to test this PR?

Pass --json to mc pipe and observe the output:

$ cat /tmp/zero.tar.gz | mc pipe --json localhost/test/zero.tar.gz
{
 "status": "success",
 "target": "localhost/test/zero.tar.gz",
 "size": 197
}

It also adds a plain text message due to the requirements of printMsg:

$ cat /tmp/zero.tar.gz | mc pipe  localhost/test/zero.tar.gz
 0 B / ? ┃░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░▓┃197 bytes -> `localhost/test/zero.tar.gz`

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[klauspost]

LGTM.

[harshavardhana]

Looks great thanks for the contribution

[fennm]

Great, thank you!