fix(mysql): Work around for Issue #2206 (ColumnNotFound error when querying)

[duelafn]

This fixes the test case in https://github.com/launchbadge/sqlx/issues/2206#issuecomment-3482364427.

I realize that this may not be the best fix for the issue, so consider this a conversation starter PR. The comments in the mysql connection/executor.rs suggest that column information may be delayed until first result, but where and how exactly that is supposed to happen wasn't clear to me and the column information is not currently being updated appropriately. This patch catches such situations and compensates. A better fix would find where the update should have happend -- I just don't know where or how to do that.

Does your PR solve an issue?

fixes #2206

Is this a breaking change?

This change may cause some code which previously returned Err(ColumnNotFound) to now return Ok(value). This is a bug fix so the user code expected to receive Ok(value) but this is technically a change in behavior.