Fix combine bug

[stackoverfloweth]

when we unified our param utilities into withParams, we also changed the logic for the combine utilities like combinePath, combineQuery, etc. Those utilities used to just spread the params together

return {
    value: newPathString,
    params: { ...parentPath.params, ...childPath.params },
}

But with the half thought of a toString() method I updated this to re-call withParams

return withParams(newPathString, { ...parentPath.params, ...childPath.params })

Even without the toString() property this felt right but caused a bug. Because withParams renames param keys to possibly start with a leading "?" it ends up being lost when we re-call withParams when combining. Therefore if you assign a custom param (anything other than String) to a route with a parent, it will just become a string param.

For this PR I decided to update the getParam utility to check for a param without "?", then check for the param with a leading "?", then use the default "String".

Alternatively I'd be happy to go back to the version we had previously where we do not re-call withParams.

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