[full-ci]Update drone starlark file

[amrita-shrestha]

Description

This is an update on drones.star file

• using drone-cancel-previous-builds
• using thegeeklab/drone-github-comment instead of jmccann/drone-github-comment for github comments
• moving docker image references to constants
• using caches images
• Do not run PHP unit tests with Oracle by default

Related Issue

• Part of issue:
• https://github.com/owncloud/QA/issues/732
• https://github.com/owncloud/QA/issues/700
• https://github.com/owncloud/QA/issues/717
• https://github.com/owncloud/QA/issues/729
• https://github.com/owncloud/QA/issues/728
• https://github.com/owncloud/core/issues/38679

[CLAassistant]

All committers have signed the CLA.

[sonarcloud[bot]]

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