addIndex doesn't work with JSONB indexes

In PostgreSQL, there's a JSONB data type that you can use, allowing you to use PostgreSQL kind of like a document database. In order to make this efficient, you can tell PostgreSQL to create indexes on keys and nested keys in JSONB documents. This can be done with:

```
CREATE INDEX "idx_TABLE_on_KEYS" ON "TABLE" ((data::jsonb->'KEY1'->>'KEY2'))
```

Using `db.addIndex`, I'd have thought I could do the following:

```
await db.addIndex(
'TABLE',
'idx_TABLE_on_KEYS',
`(data->'KEY1'->>'KEY2')`
);
```

To produce the same index as the above SQL. However, it turns out that `db.addIndex` automatically (and perhaps sensibly) attempts to escape the values you're passing, which means you get the following query being executed:

```
CREATE INDEX "idx_TABLE_on_KEYS" ON "TABLE" ("(data->'KEY1'->>'KEY2')")
```

The additional quotes in this case actually break the creation of the index.

```
> [ERROR] AssertionError [ERR_ASSERTION]: ifError got unwanted exception: column "(data->'KEY1'->>'KEY2')" does not exist
```

I'm not sure what the right fix is, but perhaps it'd be an idea to allow the user to say "actually, I know what I'm doing, please don't escape this" whilst giving the default of escaping column names.

Thoughts?

---
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