A.F....PS. [ZBXNEXT-282] implemented additional options and HTTP header support for web scenarios

Before the change:
- There was no way to control the HTTP headers used when monitoring web applications.

After tha change:
- It's possible to specify the used HTTP headers as well as SSL verification options, whether to follow redirects and whether to retrieve the whole body of the response, or just the headers. Additionally, the length of the step URL has been increased to 2048 characters.