Merge 'Fix rowid generation' from Nikita Sivukhin

Fix panic in case when table has row with rowid equals to `-1`
(`=u64::max`)
```sql
limbo> CREATE TABLE t(x INTEGER PRIMARY KEY)
limbo> INSERT INTO t VALUES (-1)
limbo> INSERT INTO t VALUES (NULL);
thread 'main' panicked at core/vdbe/mod.rs:2499:21:
attempt to add with overflow
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

Reviewed-by: Pere Diaz Bou <pere-altea@homail.com>

Closes #868

core/vdbe/mod.rs

@@ -2496,7 +2496,11 @@ fn get_new_rowid<R: Rng>(cursor: &mut BTreeCursor, mut rng: R) -> Result<CursorR
         CursorResult::Ok(()) => {}
         CursorResult::IO => return Ok(CursorResult::IO),
     }
-    let mut rowid = cursor.rowid()?.unwrap_or(0) + 1;
+    let mut rowid = cursor
+        .rowid()?
+        .unwrap_or(0) // if BTree is empty - use 0 as initial value for rowid
+        .checked_add(1) // add 1 but be careful with overflows
+        .unwrap_or(u64::MAX); // in case of overflow - use u64::MAX
     if rowid > i64::MAX.try_into().unwrap() {
         let distribution = Uniform::from(1..=i64::MAX);
         let max_attempts = 100;

tests/integration/functions/test_function_rowid.rs

@@ -81,3 +81,42 @@ fn test_last_insert_rowid_basic() -> anyhow::Result<()> {
     do_flush(&conn, &tmp_db)?;
     Ok(())
 }
+
+#[test]
+fn test_integer_primary_key() -> anyhow::Result<()> {
+    let _ = env_logger::try_init();
+    let tmp_db = TempDatabase::new("CREATE TABLE test_rowid (id INTEGER PRIMARY KEY);");
+    let conn = tmp_db.connect_limbo();
+
+    for query in &[
+        "INSERT INTO test_rowid VALUES (-1)",
+        "INSERT INTO test_rowid VALUES (NULL)",
+    ] {
+        let mut insert_query = conn.query(query)?.unwrap();
+        loop {
+            match insert_query.step()? {
+                StepResult::IO => tmp_db.io.run_once()?,
+                StepResult::Done => break,
+                _ => unreachable!(),
+            }
+        }
+    }
+    let mut rowids = Vec::new();
+    let mut select_query = conn.query("SELECT * FROM test_rowid")?.unwrap();
+    loop {
+        match select_query.step()? {
+            StepResult::Row(row) => {
+                if let Value::Integer(id) = row.values[0] {
+                    rowids.push(id);
+                }
+            }
+            StepResult::IO => tmp_db.io.run_once()?,
+            StepResult::Interrupt | StepResult::Done => break,
+            StepResult::Busy => panic!("Database is busy"),
+        }
+    }
+    assert_eq!(rowids.len(), 2);
+    assert!(rowids[0] > 0);
+    assert!(rowids[1] == -1);
+    Ok(())
+}