statement: reset parameters

[muzarski]

Implemented cass_statement_reset_parameters. It should clear a vector of bound values, and resize it, filling it with Unset values.

Pre-review checklist

• [x] I have split my patch into logically separate commits.
• [x] All commit messages clearly explain what they change and why.
• [x] PR description sums up the changes and reasons why they should be introduced.
• ~[ ] I have enabled appropriate tests in .github/workflows/build.yml in gtest_filter.~
• ~[ ] I have enabled appropriate tests in .github/workflows/cassandra.yml in gtest_filter.~