nextra closes #4850: fix non informative error output for bad meta field when using `z.prettifyError` on parsed `z.union` schema

Why:

Closes: #4850

What's being changed (if available, include any code snippets, screenshots, or gifs):

I've made the same safeParse checks, just for each type, one by one, thus the prettify can do its thing since parse response is not from union. This is how it looks with fix.

z.prettifyError doesn't work well with unions, because it is reporting ton of issues for each union it checks, here is a simple example, where it just pulls out the message: Invalid input at the end (same issue as here):

Check off the following:

[ ] I have reviewed my changes in staging, available via the View deployment link in this PR's timeline (this link will be available after opening the PR).