Fix to #33443 - JSON path is not properly formatted

[maumar]

Queries extracting data from JSON properties containing special characters must escape references to those properties in JSON path. Moreover, the values we use in JSON paths must correspond to how we store those properties in database. When we serialize JSON-mapped entity into JSON string, many special (unicode) characters are stored in the \uxxxx form. Lastly in the shaper, when reading json data from the stream we need to make sure to correctly match the property names using Utf8JsonReader. ValueTextEquals un-escapes the property names before comparison, the Span representing the property name must also be un-escaped.

Fixes #33443

[roji]

This is tricky stuff....! LGTM (modulo nits/small stuff below).

I'm a bit worried about unescaped JSON that users put in their databases (without going through our SaveChanges). For people doing that, this PR will be a breaking change - the new query and shaper will start failing, if I understand correctly. I still think this is correct as our stuff should work consistently with itself, and we currently save escaped JSON to the database, but this may mean that we should implement #32152 for 9.0 as well, since that would give users a way forward (i.e. they'd disable escaping throughout our entire stack).

Another reason to do #32152 for 9.0 is to make sure the API design here is right and allows opting out of escaping (e.g. in RelationalSqlGenerationHelper).

[magahl]

We had an existing model that had a string property (wich was serialized json) in a Json model. Before it encoded it with a \" but now it will be a \\u0022.

When i send back my data to the client (Blazor Server) for DeSerialization it now crashes. since the "string" property contains \u0022 instead of ".

I have searched the internet for an reason and this is the best lead so far, but im not certain this is the cause. All we really have done is upgrade the framework to net 9 RC1

Code used to dersilize:
var model = JSonSerializer.Serialize<Model>(jsonString)