addedd support for sql.Null types

[m-pavel]

Description

Bypass nil value types to the API call so the server can call procedure/function properly.
Fixes #831

Checklist

• Code compiles correctly
• Run make fmt to fix inconsistent formats
• Run make lint to get lint errors and fix all of them
• Created tests which fail without the change (if possible)
• All tests passing
• Extended the README / documentation, if necessary

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[m-pavel]

I have read the CLA Document and I hereby sign the CLA

[sfc-gh-dszmolka]

thank you @m-pavel for your contribution here ! in the end we ended up going with a different solution which has been implemented with #844 and released as part of driver version 1.6.23. since it's implemented, marking this PR as closed for now.