feat!: change default read_consistency_interval=5s (#2281)

Previously, when we loaded the next version of the table, we would block
all reads with a write lock. Now, we only do that if
`read_consistency_interval=0`. Otherwise, we load the next version
asynchronously in the background. This should mean that
`read_consistency_interval > 0` won't have a meaningful impact on
latency.

Along with this change, I felt it was safe to change the default
consistency interval to 5 seconds. The current default is `None`, which
means we will **never** check for a new version by default. I think that
default is contrary to most users expectations.

nodejs/examples/basic.test.ts

@@ -202,5 +202,35 @@ test("basic table examples", async () => {
       // --8<-- [end:create_f16_table]
       await db.dropTable("f16_tbl");
     }
+    const uri = databaseDir;
+    await db.createTable("my_table", [{ id: 1 }, { id: 2 }]);
+    {
+      // --8<-- [start:table_strong_consistency]
+      const db = await lancedb.connect({ uri, readConsistencyInterval: 0 });
+      const tbl = await db.openTable("my_table");
+      // --8<-- [end:table_strong_consistency]
+    }
+    {
+      // --8<-- [start:table_eventual_consistency]
+      const db = await lancedb.connect({ uri, readConsistencyInterval: 5 });
+      const tbl = await db.openTable("my_table");
+      // --8<-- [end:table_eventual_consistency]
+    }
+    {
+      // --8<-- [start:table_no_consistency]
+      const db = await lancedb.connect({ uri, readConsistencyInterval: null });
+      const tbl = await db.openTable("my_table");
+      // --8<-- [end:table_no_consistency]
+    }
+    {
+      // --8<-- [start:table_checkout_latest]
+      const tbl = await db.openTable("my_table");
+
+      // (Other writes happen to test_table_async from another process)
+
+      // Check for updates
+      tbl.checkoutLatest();
+      // --8<-- [end:table_checkout_latest]
+    }
   });
 });