test: add sustained workload scenario to the performance test suite

[michaelawyu]

What type of PR is this?

/kind test

What this PR does / why we need it:

This PR adds a sustained workload scenario to the performance test suite.

Which issue(s) this PR fixes:

N/A

Requirements:

• run make reviewable for basic local test
• Read and followed fleet-networking's Code of conduct.
• uses conventional commit messages
• includes documentation
• [N/A] adds unit tests

How has this code been tested

N/A

Special notes for your reviewer

Do not merge until PR #143 is merged.

[codecov]

Codecov Report

Merging #144 (795f9d8) into main (5e3ea49) will decrease coverage by 0.04%.
The diff coverage is 97.43%.

❗ Current head 795f9d8 differs from pull request most recent head d99db56. Consider uploading reports for the commit d99db56 to get more accurate results

@@            Coverage Diff             @@
##             main     #144      +/-   ##
==========================================
- Coverage   78.95%   78.91%   -0.05%     
==========================================
  Files          20       20              
  Lines        2737     2727      -10     
==========================================
- Hits         2161     2152       -9     
  Misses        457      457              
+ Partials      119      118       -1     

Impacted Files	Coverage Δ
pkg/controllers/member/serviceexport/controller.go	78.32% <96.87%> (ø)
...rollers/member/internalserviceexport/controller.go	83.84% <100.00%> (ø)
pkg/controllers/hub/serviceimport/controller.go	72.85% <0.00%> (-6.43%)	⬇️
...ontrollers/hub/internalserviceimport/controller.go	75.79% <0.00%> (-1.59%)	⬇️
pkg/controllers/member/endpointslice/controller.go	79.49% <0.00%> (-1.44%)	⬇️
...ntrollers/member/endpointsliceimport/controller.go	79.92% <0.00%> (+0.39%)	⬆️
pkg/controllers/multiclusterservice/controller.go	84.17% <0.00%> (+1.76%)	⬆️
...rollers/member/internalmembercluster/controller.go	72.72% <0.00%> (+1.94%)	⬆️
... and 1 more

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[zhiying-lin]

few minor comments