Add sending urls in packets

[wblachowski]

This change reintroduces sending multiple URLs in one message to collectors in order to boost performance.

Description

Changes made as a part of rerun functionality in #412 (in CollectDispatcher class among others) removed the possibility to send multiple URLs in a single message received by CollectorMessageListener. This affected the performance because there is a new web driver created for each received message and this operation is resource consuming. By grouping multiple URLs in a single message it is possible to reuse a single web driver many times.

I made some measurements using a dummy suit with 2 tests, each containing 10 URLs pointing to a server running on my local machine. The average times of 3 test runs for different URL package sizes are present in the following table:

Package size	Average suite runtime (in seconds)
1	33.22
3	24.07
6	19.22
9	27.04

Please keep in mind that only URLs within a single test are grouped (because each test can have different proxy setting etc.) so the performance gain is heavily dependent on the suit being tested,

Motivation and Context

Closes #431

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• My code follows the code style of this project.
• I have reviewed (and updated if needed) the documentation regarding this change

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I hereby agree to the terms of the AET Contributor License Agreement.

[annabudziszewska]

Tested and accepted
Version: 3.3.1.SNAPSHOT