Consider revising credit default higher

[michaelklishin]

Is your feature request related to a problem? Please describe.

This is neither a bug nor a feature request but it can potentially safe some confusion.

In #750, you can see that a couple of unacknowledged message values, namely 100 but also 10,
produce a surprising message rate drop.

Digging in has led me to

1. Discover that ProducerBuilder#batchSize defaults to 100
2. Dynamic batching Add dynamic-batch publishing option #649
3. Dynamic batching enabled by default in recent versions Use dynamic batch publishing by default #671

All of those improvements are great but we might have to revisit some of our batching- and credits-related defaults because regardless of how impractical (considering the kind of throughput streams can handle when they are not resource-constrained), a maximum unacknowledged value of 10 is still a setting someone might choose to compare.

Describe the solution you'd like

Perhaps the default credit should match the default batch size, that is, be set to 100? Or both should be set to 1000 by default?

Stream PerfTest uses 20K for its default.

Describe alternatives you've considered

No response

Additional context

See #750.