Support target_throughput=none for big5

[jed326]

Description

Add support for target_throughput:none to big5 workload.

Tested on cli, all following scenarios pass:

./Library/Python/3.9/bin/opensearch-benchmark execute-test --workload=big5 --pipeline=benchmark-only --test-procedure=test --target-hosts=opense-clust-tFncA2PxB4im-27a28ec1e07ac294.elb.us-east-1.amazonaws.com:80 --kill-running-processes --workload-params="target_throughput:none,warmup_iterations:5,test_iterations:5"

./Library/Python/3.9/bin/opensearch-benchmark execute-test --workload=big5 --pipeline=benchmark-only --test-procedure=test --target-hosts=opense-clust-tFncA2PxB4im-27a28ec1e07ac294.elb.us-east-1.amazonaws.com:80 --kill-running-processes --workload-params="target_throughput:0,warmup_iterations:5,test_iterations:5"

./Library/Python/3.9/bin/opensearch-benchmark execute-test --workload=big5 --pipeline=benchmark-only --test-procedure=test --target-hosts=opense-clust-tFncA2PxB4im-27a28ec1e07ac294.elb.us-east-1.amazonaws.com:80 --kill-running-processes --workload-params="target_throughput:4,warmup_iterations:5,test_iterations:5"

/Library/Python/3.9/bin/opensearch-benchmark execute-test --workload=big5 --pipeline=benchmark-only --test-procedure=test --target-hosts=opense-clust-tFncA2PxB4im-27a28ec1e07ac294.elb.us-east-1.amazonaws.com:80 --kill-running-processes --workload-params="warmup_iterations:5,test_iterations:5"

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[jed326]

Closing this out as I am using target_throughput:"" in https://github.com/opensearch-project/opensearch-build/pull/4739