Allow writing multiple default namespace prefixes

When using `jackson-dataformat-xml` and serialising an object with multiple default namespaces, all namespaces other than the first have their prefix auto-generated.

E.g. I want this:
```xml

```
But get this:
```xml

```

Based on [this comment](https://github.com/FasterXML/woodstox/blob/main/src/main/java/com/ctc/wstx/sw/RepairingNsStreamWriter.java#L520-L530) in `RepairingNsStreamWriter`, I'd like to introduce a new [woodstox specific property](https://github.com/FasterXML/woodstox/wiki/Configuring-Woodstox-III-%E2%80%90-Woodstox%E2%80%90Specific-Properties#woodstox-specific-output-properties-formatting) to allow the other option of the suggested functionality: to allow elements to override the default namespace.

The behaviour to generate prefixes automatically appears to get triggered because jackson doesn't invoke the `XMLStreamWriter.writeStartElement()` method using a prefix. This makes sense as jackson doesn't have support for defining namespace prefixes for xml.

I'm happy to have a go at implementing this in a PR if it's functionality you think would suit the project.

I haven't really considered what the behaviour should look like for attributes, and having a cursory play around adding `@JacksonXmlProperty(isAttribute = true, namespace = NS1)` onto my fields isn't giving much clarification but I'm happy to keep digging if you are open to adding support for this.