Widgets exacerbate the lowerCamelCase mixed with snake_case problem

```json
{
"action": "set_always_on_screen",
"api": "fromWidget",
"data": {
"value": true
},
"requestId": "generated-id-1234",
"widgetId": "20200827_WidgetExample"
}
```

`requestId` is lowerCamelCase whereas the `set_always_on_screen` action is snake_case.

Start with the JSON example in issue #689 and the Matrix protocol specification sections defining widget actions and fields. Check how `set_always_on_screen`, `requestId`, and `widgetId` are specified, then determine the scope of the naming inconsistency and what documentation updates would be needed for a consistent convention.

Written by the indexing model from the issue text.