?fields should support fully-qualifying

[svix-jbrown]

Use case

Using ?fields with joins doesn't work if the same column name (e.g., id) occurs in multiple tables, because ?fields expands to non-qualified names, so the query fails with ambiguous identifier 'id'

client.query("SELECT ?fields FROM table1 JOIN table2 ON table1.foo = table2.bar")
   .fetch_all()
   .await?;

### Describe the solution you'd like

some kind of API to tell clickhouse how to fully-qualify `?fields`. Maybe something like

client.query("SELECT ?fields ...")
.with_fields_qualified_by("table1")
.fetch_all()

### Describe the alternatives you've considered

For now I'm just writing out the fields by hand by reading `Self::COLUMN_NAMES` in a loop, but because none of the clickhouse escaping functions are public this is kind of unsafe and dumb

### Additional context