Fix --number-of-docs bug in create-workload

[IanHoang]

Description

Currently, there's a bug in create-workload when users specify the number of docs to extract from an index. Addressing the fix in this PR. This PR also adds more error handling and warnings to streamline user experience.

Issues Resolved

#658

Testing

• New functionality includes testing

Tested with these scenarios:

• Running create-workload with 2+ number of docs entries
• Testing number of docs entry with 0 or less docs
• Testing number of docs entry with less than 1K docs
• Testing number of docs entry that does not exist in the cluster

(.venv) hoangia@80a9971b1103 opensearch-benchmark % opensearch-benchmark create-workload --target-hosts=XXXXXX --client-options=basic_auth_user:'XXXXXX',basic_auth_password:'XXXXXX' --indices=movies-1000,movies-2000,nyc_taxis  --output-path=~/Desktop/ --workload=test-workload --number-of-docs="movies-2000:1500 nyc_taxis:1500"

   ____                  _____                      __       ____                  __                         __
  / __ \____  ___  ____ / ___/___  ____ ___________/ /_     / __ )___  ____  _____/ /_  ____ ___  ____ ______/ /__
 / / / / __ \/ _ \/ __ \\__ \/ _ \/ __ `/ ___/ ___/ __ \   / __  / _ \/ __ \/ ___/ __ \/ __ `__ \/ __ `/ ___/ //_/
/ /_/ / /_/ /  __/ / / /__/ /  __/ /_/ / /  / /__/ / / /  / /_/ /  __/ / / / /__/ / / / / / / / / /_/ / /  / ,<
\____/ .___/\___/_/ /_/____/\___/\__,_/_/   \___/_/ /_/  /_____/\___/_/ /_/\___/_/ /_/_/ /_/ /_/\__,_/_/  /_/|_|
    /_/

[INFO] You did not provide an explicit timeout in the client options. Assuming default of 10 seconds.
[INFO] Connected to OpenSearch cluster [69622e766ec7eb17f038aed664796847] version [2.5.0].

A workload already exists at /Users/hoangia/Desktop/test-workload. Would you like to remove it? (y/n): y
[INFO] Removing workload of the same name.
Extracting documents for index [movies-1000] for test mode... 1000/1000 docs [100.0% done]
Extracting documents for index [movies-1000]...               1000/1000 docs [100.0% done]
Extracting documents for index [movies-2000] for test mode... 1000/1000 docs [100.0% done]
Extracting documents for index [movies-2000]...               1500/1500 docs [100.0% done]
Extracting documents for index [nyc_taxis] for test mode...   1000/1000 docs [100.0% done]
Extracting documents for index [nyc_taxis]...                 1500/1500 docs [100.0% done]

[INFO] Workload test-workload has been created. Run it with: opensearch-benchmark --workload-path=/Users/hoangia/Desktop/test-workload

-------------------------------
[INFO] SUCCESS (took 4 seconds)
-------------------------------

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[gkamat]

fIs this the case where the user provides multiple entries in a single arg within shell quotes?

--number-of-docs "x:3 y:4 z:8"

In that case, nargs should be 1, not +.
To handle both cases with +, this code should be activated only when len(values) is 1. In other cases, this should fall back to the earlier mode of processing.

[IanHoang]

Got it. Will implement it to where it handles both use cases.