Merge env and e2e tests

[a-thaler]

Description
For the telemetry-manager there are 3 different kind of test realized: unit test, env test, e2e test
It is hard to grasp when to write an env test and when to write an e2e test. ALso the used technology is different (one is a full integration test while the other mocks an apiserver)
To keep it simple, the team decided to remove the middle test layer.

Criterias

• Unit tests are not starting an APIServer anymore
• Installing env test binary is removed from make targets
• No loss in test coverage
• The test strategy document is updated to reflect the change (https://github.com/kyma-project/telemetry-manager/blob/main/docs/contributor/testing.md)

[shorim]

TODO list:

• Migrate env tests for Telemetry controller: test: Migrate Telemetry env tests to e2e tests #1031
• Migrate env tests for TracePipeline and MetricPipeline controllers:
  - test: Migrate traces and metrics env tests to e2e tests #1057
  - test: Improve check for existence of OwnerReference in e2e tests #1062
  - test: Convert new OTel Collector basic auth/custom header/mtls E2E tests to unit tests #1063
• Delete env tests for LogParser controller test: Remove env tests for LogParser #1071
• Migrate env tests for LogPipeline controller:
  - test: Migrate logs env tests to e2e tests #1076
  - chore: Rewrite LogPipeline Reconciler unit tests  #1121
• Replace LogPipeline webhook envtests with unit tests test: Replace LogPipeline webhook envtests with unit tests #1110
• Remove env tests from test strategy documentation and remove env test binary dependency from Makefile chore: Clean up env test dependency and documentation #1118