4.1.3: Concurrency limits module, and support in Helidon WebServer

[barchetta]

Backport of #9295 to Helidon 4.1.3

Description

Resolves #8897
Resolves #9229

Documentation

This PR introduces

• a new module common/concurrency/limits that provides API and SPI for concurrency limit implementations, and a couple of default implementations (AIMD, Fixed).
• a new module webserver/concurrency-limits that provides feature with a filter to impose limits within a filter in routing
• update of webserver/webserver to use a Limit instead of a Semaphore in connection handlers (backward compatible)

Configuration reference will be in the generated documentation.

Configure limits on WebServer

This will configure limit for a server listener (configurable per listener), enforced on the connection level (i.e. outside of routing and filters).

The default behavior is the same (unlimited).
If server.max-concurrent-requests is configured (value is not -1), it will be used and concurrency-limit configuration for the listener will be ignored.

Configuration:

server:
  port: 8080
  concurrency-limit:
    aimd: # `limit type`
      # AIMD limit configuration

Configure limits for routing

This will configure limit for as a server feature, enforced in an HTTP filter.
Configuration:

server:
  features:
    limits: # the feature is called `limits`
      enabled: true
      concurrency-limit: # `limit` configuration of the `limits` server feature
        fixed: # `limit type`
          permits: 1
          queue-length: 10