[full-ci]Use directory references from global dir variable in drone.star file

[amrita-shrestha]

Description

it is better to use directory references from the dir var, rather than using the hard-coded values in every use case. Dropped 7.3 PHP because owncloud doesn't support 7.3 PHP anymore

Related Issue

• https://github.com/owncloud/QA/issues/734#issue-1173320353

Motivation and Context

How Has This Been Tested?

• CI

Screenshots (if appropriate):

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
• [x] Tests only (no source changes)

Checklist:

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