test: delete test fixtures after test run.

[autonomousapps]

Just to see perf information in build scans.

[github-actions]

❌ Test workflow failed:

* Root buildHealth         : https://gradle.com/s/hsz4bdnyv5zvw
* TestKit buildHealth      : https://gradle.com/s/4j3owt6dx5dkg
* Non-functional tests     : https://gradle.com/s/qvveyszogsyio
* TestKit check            : https://gradle.com/s/tsrpnjyvhh3qm
* JVM functional tests     : https://gradle.com/s/j63qgaypetydk
* Android functional tests : https://gradle.com/s/4ugjmzdpscj3c

[autonomousapps]

Lots of memory used: https://scans.gradle.com/s/4ugjmzdpscj3c/performance/build#memory-g-1-old-gen