[WIP] Guzzle6 for core

[phil-davis]

Description

• update dependency for Guzzle to 6.5
• get adjusted code from old PR [WIP] Guzzle6 for core #38266 (that itself came from PRs [WIP] Guzzle6 for core #37011 Acceptance Tests for case-sensitive file names #32357 )
• do whatever is needed to make it work
• enable Tests/TestHelpers/Unit tests again (they rely on having guzzle6 since the acceptance test code was updated to guzzle6)
• Update guzzle and other dependencies in apps/files_external/3rdparty

This is a recreation of PR #38266

Related Issue

Motivation and Context

Guzzle5 does not have official support on PHP 7.4 and probably never will have. Guzzle5 works on PHP 7.4
For future PHP versions (e.g. PHP 8.0) we might be forced to do this Guzzle update.

Note1: if we do this then apps that use Guzzle5 will also need updating to Guzzle6 and coordinated release of core and app versions etc.

Note2: guzzle is actually up to release https://github.com/guzzle/guzzle/releases/tag/7.2.0 - so if we bump guzzle we might want to bump it all the way to major version 7.

How Has This Been Tested?

CI

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Database schema changes (next release will require increase of minor version instead of patch)
• Breaking change (fix or feature that would cause existing functionality to change)
• Technical debt
• Tests only (no source changes)

Checklist:

• Code changes
• Unit tests added
• Acceptance tests added
• Documentation ticket raised:
• Changelog item, see TEMPLATE

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would create a changelog item based on your changes.

[phil-davis]

Federated acceptance tests are failing.

sqlite+scality unit tests with messages like TypeError: Argument 3 passed to GuzzleHttp\Client::request() must be of the type array, object given, called in /drone/src/lib/composer/guzzlehttp/guzzle/src/Client.php on line 95

Needs investigating when someone wants to move forward with this.

[phil-davis]

This is here as a "record" of past code for updating Guzzle from v5 to v6. It should provide a good starting point if someone does this some day.

[JammingBen]

Superseded by #39368.