Move to more standard CI pipelines

[juliusknorr]

• chore: Move to more standard ci pipelines for eslint, stylelint, php-cs-fixer, psalm, info.xml
• style: Apply php-cs-fixer changes
• chore: Remove some deprecations in Application.php

Deprecation to file as issue to drop once we increase minimum supported versions:

INFO: DeprecatedMethod - lib/Migration/EditorHint.php:33:32 - The method OCP\IConfig::getAppValue has been marked as deprecated (see https://psalm.dev/001)
INFO: DeprecatedMethod - lib/Service/SettingsService.php:75:29 - The method OCP\IConfig::getAppValue has been marked as deprecated (see https://psalm.dev/001)
INFO: DeprecatedMethod - lib/Service/SettingsService.php:90:35 - The method OCP\IConfig::getAppValue has been marked as deprecated (see https://psalm.dev/001)
INFO: DeprecatedMethod - lib/Service/SettingsService.php:197:10 - The method OCP\Util::getVersion has been marked as deprecated (see https://psalm.dev/001)

Standardizing the phpunit test execution has been left out as it is more of an integration test that currently requires quite a lot of manual setup.

• [ ] Adjust branch requirements to main branch once this PR is merged