Re-export ParseIrOpt to ease custom implementations of FromValue

[LeoniePhiline]

Trying to implement FromValue for a custom type, based on ParseIrOpt<bool>, I noticed that ParseIrOpt is not re-exported.

Needing to add mysql_common as direct dependency causes overhead, as compatible version updates must be coordinated. (For example, the current mysql_async 0.36 requires mysql_common 0.35, while a newer mysql_common 0.36 would be available.)

Re-exporting ParseIrOpt allows users of mysql_async to implement FromValue for custom types without needing to manage this added dependency.

[LeoniePhiline]

CI failure https://dev.azure.com/aikorsky/mysql%20Rust/_build/results?buildId=881&view=logs&j=8ce5181b-5fcc-505f-e6e7-de201e0f224e&t=859e6757-1b19-5d33-c315-81715657f0f4 seems unrelated.