[V2] Add warning for invalid max-items value

[aemous]

Description of changes: Explicitly warn users that we do not support non-positive values for the max-items global pagination argument.

Example output:

aws s3api list-objects --bucket bucket-123 --max-items 0
2024-08-08 12:11:58,993 - awscli.customizations.paginate - CRITICAL - Non-positive values for --max-items are unsupported and may yield undefined behavior.

{
    "RequestCharged": null
} 

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[aemous]

Iterated on all requested feedback. If this looks good I'll open a V1 version with the same code. @hssyoo

[aemous]

Iterated on all requested feedback. If this looks good I'll open a V1 version with the same code. @hssyoo