Read-write operations flushing inside batch environment

[cieplypolar]

As of PR #1684, read-write operations are allowed to immediately flush command encoder during batch invocation. Personally, I lean towards forbidding this.

Outside the batch environment, there is no reason for read-write operations to flush (since everything is flushed immediately anyway).

It feels odd to enter a batch and then have it interrupted by a read-write operation. User should either perform operation right after the batch or start a new batch for it.

[iwoplaza]

Read operations are asynchronous, so it naturally suggests to users that there's no way to start and complete a read within the same batch. I would argue it's important to permit write operations to continue working in batch mode, as when writing a piece of code (especially reusable code), we're not sure whether we're running in a batched environment or not, and imo, we shouldn't have to worry about it.

function computeFoo() {
  // This code can be run inside a tgpu.batch callback
  param.write(123);
  action.dispatch();
}

For more exotic use-cases, like enqueueing a read during a batch and completing it later, I think it's still valid to allow it.

[cieplypolar]

You convinced me with reusability. Read-write operations flush encoders 🚰