Make opencti URL and token configurable via env var for examples and tests

[aHenryJard]

Please replace every line in curly brackets { like this } with appropriate answers, and remove this line.

Problem to Solve

• When running example locally with a custom opencti instance, it's required to change code in python file.

Current Workaround

{ Please describe how you currently solve or work around this problem, given OpenCTI's limitation. }

Proposed Solution

• Make Opencti URL and OpenCTI token configurable with env var.

Additional Information

{ Any additional information, including logs or screenshots if you have any. }