create Map<K, T>::query_all

function signature should probably look something like:
```rust
impl<'a, K, T> Map<'a, K, T>
where
T: Serialize + DeserializeOwned,
K: PrimaryKey<'a>,
{
pub fn query_all(
&self,
querier: &QuerierWrapper,
remote_contract: Addr,
order: Order // Not sure this is required
) -> StdResult> {
...
}
}
```

The purpose of this function is to allow the querying of external contracts, and should function similarly to the existing Map::query.

Start by reading the existing Map::query implementation and the surrounding Map API. Determine how querying an external contract should return all values and whether ordering is required. Done means a public query_all method matching the requested signature and behavior, with coverage in the project's existing tests if applicable.

Written by the indexing model from the issue text.