Description of problem:

The following difference exists between Logging 5.9 and 6.0.

• Logging 5.9 and eariler: "spec.tuning.delivery" is a global parameter. This has an effect for any log types including syslog.
• Logging 6.0: The parameter was re-defined[1] as log type's specific parameter("spec.outputs[].<log type>.tuning.deliveryMode"). Some log types have this but syslog doesn't have.

As a result, we are no longer able to set the equivalent setting of "spec.tuning.delivery: AtLeastOnce" for syslog in Logging 6.0.
This is a big regression for users who use syslog forwarding.

[1] https://github.com/openshift/cluster-logging-operator/pull/2762/files#diff-4749b2553f93d0fa25f19c74b7fad9dc691f10c0bf9c8f4b46ab0681c4a9560dR179

Version-Release number of selected component (if applicable):

cluster-logging.v6.0.0

How reproducible:

Always

Additional information:

In Logging 5.9, we can set "spec.tuning.delivery: AtLeastOnce" for syslog.
We also confirmed that the setting is reflected to vector.toml as follows in Logging 5.9.

[sinks.output_syslog.buffer]
type = "disk"         <= settings added by atLeastOnce
when_full = "block"   <= settings added by atLeastOnce
max_size = 268435488  <= settings added by atLeastOnce