Introduce basic integration test of docker-registry on btp platform

Description Implement an e2e integration test for docker-registry's basic flow.

[x] The test should verify if a custom image could be pushed to docker-registry via external https endpoint (via docker CLI)
[x] The test should verify if a workload could be scheduled using image stored in internal docker registry and using (internal) image pull secret provided by the docker registry operator
[x] The test should be executed whenever a PR is merged into main branch ( part of "post-submit")
[ ] ... (and part of "release" workflows)
[x] The test should use automation tooling designed to automate CI on top of btp platform resources (i.e bot user against a global account on canary landscape).
[x] The test should clean up btp resources via btp remove accounts/subaccount --subbaccount {ID} --force
[x] The test should ensure that all required binaries (kyma@v3, btp CLIs) are downloaded
[x] the test job configuration should include: target btp landscape, target btp global account, bot user credentials (password read from sap vault), target custom IAS tenant, subaccount region, kyma plan and region. (see config used in the poc)
[x] the test job should allow executing multiple runs in parallel - the resource names should be generated in a unique fashion (idea: incorporating hash of commit)

Reason We need an automated test that executes basic flow and protect us from regressions.

kyma-project / docker-registry