log verbosity values should match those in kick

The log verbosity values, as seen in https://github.com/Autodesk/arnold-usd/blob/25c21224517ce8da3c37c826c59ad8dc60487f14/libs/render_delegate/render_delegate.cpp#L403 do not match those of kick. For instance, `kick -v 3` has AI_LOG_STATS enabled but that is not enabled until `4` in the arnold-usd code.

Start at libs/render_delegate/render_delegate.cpp around line 403 and compare its verbosity mapping with the behavior of kick. Check specifically that kick -v 3 enables AI_LOG_STATS while the USD render delegate currently waits until 4. Done means the verbosity values match kick consistently.

Written by the indexing model from the issue text.