Interpret `?` as a parameter only if `.bind` was called at least once

Related to https://github.com/ClickHouse/clickhouse-rs/pull/154

Considering this query:

```rs
client
.query("SELECT 1 FROM test WHERE a IN 'a?b'")
.fetch_one::()
.execute()
.await?;
```

Currently, an unescaped `?` is still considered a missing parameter; after the fix, the query should be written as:

```rs
client
.query("SELECT 1 FROM test WHERE a IN 'a??b'")
.fetch_one::()
.execute()
.await?;
```

This might be problematic if a query is pre-generated elsewhere (file, etc) and contains question marks, but we did not want to do any client-side binding.

Start by reading the issue examples and the linked pull request 154; the payload does not name an implementation file or test. Trace how query strings and bind calls handle `?`, then verify that unbound queries permit literal question marks while bound queries still require escaping.

Written by the indexing model from the issue text.