Methods in Json re-create JsonProvider on each execution, Json should cache the result of JsonProvider.provider()

Nobody has claimed this yet.

The methods in Json use `JsonProvider.provider()` and this **re-creates the JsonProvider on each execution**.

The javadoc for `JsonProvider.provider()` suggests that the caller should cache the resulting `JsonProvider` and `jakarta.json.Json` does not do this, so I think this is a bug.

For example, in Json we see:

```java
/**
* ...
*/
public static JsonParser createParser(Reader reader) {
return JsonProvider.provider().createParser(reader);
}

/**
* ...
*/
public static JsonParser createParser(InputStream in) {
return JsonProvider.provider().createParser(in);
}
```

In the javadoc for `JsonProvider.provider()` is says:
> _"Creates a JSON provider object. ... **Users are recommended to cache the result of this method**."_

I believe that means that `Json` should be changed to indeed cache the result of `JsonProvider.provider()`.

Start in the Json class at the createParser(Reader) and createParser(InputStream) entry points, then inspect the other methods that call JsonProvider.provider(). Confirm the provider is cached as recommended by JsonProvider.provider() and that the Json methods use the cached result consistently.

Written by the indexing model from the issue text.