Double check default values of configurable and statically configured values

[tillrohrmann]

Before handing Restate out to users, we should double check the default values for configurable and statically configured values. Examples:

• num partitions
• channel size
• Tokio threads
• Concurrency limits
• etc.

Ideally, we have some way to measure the impact of different configurations.

[igalshilman]

Since we are already handing the binary to folks, can we please bump the default_concurrency_limit it is currently 1k, which is very low.
Let's set to the 32k at least, if not 100k or 1M.

What kind of resources are associated with each concurrency slot at the moment?
I'd assume:

• An entry in an Ingress map
• A oneshot for the response
• An entry in the invoker's map
• 3 Futures that are associated with each request slot?
• Possibly a file descriptor?