Merging multiple ui-base nodes

### Current Behavior

When importing a `ui-base` node, we keep the oldest node if one already exists. To date, this hasn't been a major issue as options are only styling-based. However, we now have the "Accept Client Data" array, which is more likely to differ `ui-base` to `ui-base`.

### Expected Behavior

Ideally, we would [support multiple UI Bases](https://github.com/FlowFuse/node-red-dashboard/issues/23), but until we can, we should probably merge these values and collate a single, long, list to ensure imported nodes work as expected.

### Steps To Reproduce

https://github.com/FlowFuse/node-red-dashboard/pull/883#discussion_r1610203782

### Environment

- Dashboard version:
- Node-RED version:
- Node.js version:
- npm version:
- Platform/OS:
- Browser:

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate