Support for variable autofill for Inline imports of clusters

Currently none of the variables from `Table` are autofilled with intellisense:
```
let start = ago(40m);
cluster("https://cluster.kusto.windows.net").database("Database").
Table
| where env_time > start
| take 10
```

Adding this would make the library extremely powerful as I often use KQL queries against multiple clusters and forwards their results to other queries using `cluster`.