studio: Don't try to send `data` events if DVC `start` event failed.

[daavoo]

When using DVCLive inside a stage being executed by dvc exp run, we still try to send data events on every step even if the start event sent by DVC failed due to misconfiguration.

From DVC side, we need to expose that the start event failed.

[daavoo]

I am no longer sure if we want to not try to send data event, at least in the current state of the client where we are not really differentiating the failure.

In some cases, start might have failed for some server error or timeout, etc, and we would actually want to try sending the data again.

Dropping p1 for now, we need to handle repeating failures in #685 so worst case scenario (i.e. auth failure) we would be sending one or a few requests that will be rejected.

[dberenbaum]

@daavoo Do you want to keep it in the backlog or should we drop it?

[daavoo]

@daavoo Do you want to keep it in the backlog or should we drop it?

I dropped it. Ideally, we should identify certain failures during start in DVC (i.e. unauthorized) where we know there is no point in trying to send data again.