Allow JsonSerializerOptions without TypeInfoResolver

[flensrocker]

I have JsonSerializerOptions which only adds some converters and set the naming policy. I don't have a source generated JsonSerializerContext and therefore no TypeInfoResolver.

When passing these options to a WithTools function, I get the exception:

JsonSerializerOptions instance must specify a TypeInfoResolver setting before being marked as read-only.

I understand that making these options read only is a good thing, but I don't understand enough about the difference to the overload of MakeReadOnly(populateMissingResolver) on the options.

I can set TypeInfoResolver = new DefaultJsonTypeInfoResolver() on my options, but that seems a bit weird.

To Reproduce
Steps to reproduce the behavior:

1. Pass a new System.Text.Json.JsonSerializerOptions() object to one of the WithTools functions.

Expected behavior
No exception should be thrown.