[Test] Use helm deployment for e2e tests

[dacappo]

Description

The integration test goal e2e-test does not come with a separate deployment anymore and expects karydia to be installed on the current cluster. The testing guideline is extended with description to use standard helm deployment with dev settings.

Checklist

Before submitting this PR, please make sure:

• [x] your code builds clean with make
• [x] your code lets succeed unit tests with make test
• [x] your code lets succeed integration tests
• [x] you have documented new or changed features