feat: support checking out a version on a branch (#3504)

### Description

Stacked on #3490. Adds an optional version to branch checkout across the
Rust core and the Python and TypeScript SDKs, so you can open a specific
version on a branch ("version V of branch B"), not just the branch's
latest version

Rust

```rust
// Open version 3 of branch "exp" (a read-only view): check out from an
// existing table, or open it directly from the connection.
let exp_v3 = table.checkout_branch("exp", Some(3)).await?;
let exp_v3 = db.open_table("items").branch("exp").version(3).execute().await?;
// checkout_latest re-attaches to the branch's writable HEAD.
exp_v3.checkout_latest().await?;

// With no branch, a version opens main at that version.
let main_v3 = db.open_table("items").version(3).execute().await?;
```

Python

```python
# Open version 3 of branch "exp" (a read-only view): check out from an
# existing table, or open it directly from the connection.
branch_v3 = await table.branches.checkout("exp", version=3)
branch_v3 = await db.open_table("items", branch="exp", version=3)
# checkout_latest re-attaches to the branch's writable HEAD.
await branch_v3.checkout_latest()

# With no branch, a version opens main at that version.
main_v3 = await db.open_table("items", version=3)
```

TypeScript

```typescript
// Open version 3 of branch "exp" (a read-only view): check out from an
// existing table, or open it directly from the connection.
const branchV3 = await (await table.branches()).checkout("exp", 3);
const opened = await db.openTable("items", undefined, { branch: "exp", version: 3 });
// checkoutLatest re-attaches to the branch's writable HEAD.
await branchV3.checkoutLatest();

// With no branch, a version opens main at that version.
const mainV3 = await db.openTable("items", undefined, { version: 3 });
```

### Testing
- Added unit tests (Rust, Python sync + async, TypeScript):
branch-scoped resolution at a version number shared with `main` and with
another branch, read-only enforcement on a pinned handle,
`checkout_latest` recovery to the branch's HEAD, fork-point reads, and
the nonexistent-version/branch error paths.
- Ran smoke tests against the Python and TypeScript SDKs on local
machine.

nodejs/src/table.rs

@@ -1190,8 +1190,18 @@ impl Branches {
     }
 
     #[napi]
-    pub async fn checkout(&self, name: String) -> napi::Result<Table> {
-        let table = self.inner.checkout_branch(&name).await.default_error()?;
+    pub async fn checkout(&self, name: String, version: Option<i64>) -> napi::Result<Table> {
+        let version = version
+            .map(|v| {
+                u64::try_from(v)
+                    .map_err(|_| napi::Error::from_reason("version must be a non-negative integer"))
+            })
+            .transpose()?;
+        let table = self
+            .inner
+            .checkout_branch(&name, version)
+            .await
+            .default_error()?;
         Ok(Table::new(table))
     }