[CPDEV-103460] Support PSS in external iperf3 plugin, and add benchmark guide

[ilia1243]

Description

• Support PSS in external iperf3 plugin, and add benchmark guide

Solution

• Added namespace to iperf3.yaml.j2 that is configured depending on PSS enforce profile.

Test Cases

TestCase 1

Steps:

1. Follow guide https://github.com/Netcracker/KubeMarine/blob/improvement/iperf_fix/documentation/internal/NetworkPerfomance.md being on any PSS profile (baseline, restricted)

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• Integration CI passed
• Unit tests. If Yes list of new/changed tests with brief description
• There is no merge conflicts

[disa1217]

@ilia1243 ,
Reviewed.