Improve Secret Management and Test Configuration Handling

[Teneroy]

Secret Management
Currently, it is really hard to update GH Action secrets as GH doesn't display the values. Hence, we need to have the same names in GH and our storage. We should never forget to update our storage if GH secret is updated.
The current existing unused secrets should be deleted too.

Improve test configuration
Currently, test configuration can be done in the .env.test which is old approach. Normally all configuration is done in config.json file.
We should set different config path in .env file, e.g. CONFIG_PATH=config/config.test.json, if we want to configure for tests in a separate file.

[mfaizanse]

• Update integration tests in pre-main.
• Update integration in release pipeline
• Validation tests
• Evaluation tests
• Update evaluation and validation tests docs
• Update github secrets doc
• Update doc indexer
• chore: updated doc_indexer github action #360 (comment)