Support urls for Postman and HAR files in API Fuzzing

Problem

Users of API Fuzzing can provide HAR and Postman files to perform testing. These files can contain secrets such as authentication tokens. One way users can avoid checking these files into the repository is providing them as URLs.

Proposal

The new csharp runner code will support HAR/Postman URLs. The worker-entry script will need to be updated to support URLs for these parameters. The current parameter validation checks for files only. Additionally, the documentation for these parameters must be updated to include the URL variant.

Support URL access to HAR and Postman files.

1. Update worker-entry to support URLs
2. Add integration tests
3. Update documentation