[BUG] Regression in default exception behavior

[dblock]

What is the bug?

In #245 we may have flipped the default exception behavior. That should be undone. We also need notes in UPGRADING and a section in the user guide on how to handle errors without exceptions.

What is the expected behavior?

Backwards-compatible behavior in 2.4.0, breaking change in 3.0.

[kimpepper]

@dblock I went with this approach originally, but since all creation of the 2.3.x Client is made using the ClientBuilder it was better to make the change there. This way we can deprecate the extra constructor arg and remove in 3.x.

[dblock]

@kimpepper Am I misunderstanding and the default with the ClientBuilder is still true? Meaning old code written like so will throw exceptions? (I only want to make sure we don't break semver).

$client = (new \OpenSearch\ClientBuilder())
   ->setHosts([getenv("ENDPOINT")])
   ->setSigV4Region(getenv("AWS_REGION"))    
   ->setSigV4CredentialProvider(true)
   ->build();

If this is the case we just need better docs explaining that ClientBuilder doesn't behave like new \OpenSearch\Client, which is a bit odd.

[kimpepper]

Looks like I missed that step. I created #251