Time travel support

Several databases and data lakes support time travel which allows historical versions of a table to be queried. Regrettably, syntax and capabilities do not seem to be terribly consistent across the various implementations.

## Querying Historical Times

This option lets a database be queried as it existed at a certain point in time. (*Question:* Is this "last version prior to the given time"? or is it an error if no snapshot exists with that exact time?)

### [Databricks](https://docs.databricks.com/gcp/en/delta/history#delta-time-travel-syntax)

```
SELECT * FROM people10m TIMESTAMP AS OF '2018-10-18T22:15:12.013Z';
```

### [Snowflake](https://docs.snowflake.com/en/sql-reference/constructs/at-before)

```
SELECT * FROM my_table AT(TIMESTAMP => 'Wed, 26 Jun 2024 09:20:00 -0700'::TIMESTAMP_LTZ);
```

### [Cockroach](https://www.cockroachlabs.com/blog/time-travel-queries-select-witty_subtitle-the_future/)

```
SELECT * FROM t AS OF SYSTEM TIME '2016-06-15 12:45:00'
```

### [DuckLake](https://ducklake.select/docs/stable/duckdb/usage/time_travel.html)

```
SELECT * FROM tbl AT (TIMESTAMP => now() - INTERVAL '1 week');
```

## Querying Specific versions

This options lets a specific "version" of a database to be queried. What exactly this means seems to depend on the database implementation in question.

### Databricks

```
SELECT * FROM people10m VERSION AS OF 123;
```

### Snowflake

Note: unclear if this is the same thing (specific versions) or different

```
SELECT * FROM my_table BEFORE(STATEMENT => '8e5d0ca9-005e-44e6-b858-a8f5b37c5726');
```

### Cockroach

Unsupported

### DuckLake

```
SELECT * FROM tbl AT (VERSION => 3);
```

issue 中未确定任何仓库文件、测试或入口点。首先比较 Databricks、Snowflake、Cockroach 和 DuckLake 的语法，并确定历史时间查询和版本查询应共享语义，还是保留为特定方言的语义。完成项应包括对受支持语法和行为范围达成一致。

由索引模型根据 Issue 内容生成。