Update .drone.star and drop PHP 7.2

[phil-davis]

Part of issue owncloud/core#39134
and owncloud/QA#687

Note: this app is not regularly maintained. So the diffs of .drone.star are big - getting it up-to-date.

[phil-davis]

Needs to wait until #846 has been merged, and until a release branch for 16.1.2 issue #837 is started...

[phil-davis]

PR #846 has been merged. Waiting for a release branch to be made...

[phil-davis]

PHP unit needs to be updated to major version 9 to match with core. If I just do that, I get:

$ composer update
Loading composer repositories with package information
Updating dependencies
Your requirements could not be resolved to an installable set of packages.

  Problem 1
    - codeception/codeception[3.1.0, ..., 3.1.3] require codeception/phpunit-wrapper >6.0.15 <6.1.0 | ^6.6.1 | ^7.7.1 | ^8.0.3 -> satisfiable by codeception/phpunit-wrapper[6.0.16, ..., 6.8.3, 7.7.1, ..., 7.8.2, 8.0.3, ..., 8.1.4].
    - codeception/phpunit-wrapper[6.0.16, ..., 6.0.21] require phpunit/phpunit >=5.7.27 <6.5.13 -> found phpunit/phpunit[5.7.27, 6.0.0, ..., 6.5.12] but it conflicts with your root composer.json require (^9.5).
    - codeception/phpunit-wrapper[6.6.1, ..., 6.8.3] require phpunit/phpunit >=6.5.13 <7.0 -> found phpunit/phpunit[6.5.13, 6.5.14] but it conflicts with your root composer.json require (^9.5).
    - codeception/phpunit-wrapper[7.7.1, ..., 7.8.2] require phpunit/phpunit 7.5.* -> found phpunit/phpunit[7.5.0, ..., 7.5.20] but it conflicts with your root composer.json require (^9.5).
    - codeception/phpunit-wrapper[8.0.3, ..., 8.1.4] require phpunit/phpunit ^8.0 -> found phpunit/phpunit[8.0.0, ..., 8.5.21] but it conflicts with your root composer.json require (^9.5).
    - Root composer.json requires codeception/codeception 3.1.* -> satisfiable by codeception/codeception[3.1.0, 3.1.1, 3.1.2, 3.1.3].

Use the option --with-all-dependencies (-W) to allow upgrades, downgrades and removals for packages currently locked to specific versions.

codeception needs to be at major version 4 in order to work with PHPunit 9. So I had to also do that. And adjust the unit test code to work with PHPunit 9.

[phil-davis]

release-16.1.2 branch has been created. The release process can happen there, and that will get merged-back in due course. I expect that CI cannot pass in that release branch because of things like phpunit 9 that is now in core master. But actually the real code in the release branch is fine to work with core 10.8.0... So the release just needs to be manually tested and can work fine with PHP 7.2 (if someone still needs that).

When the release is done, we will have to sort out merging-back the changelog... that is in the release branch.