Riptide does not respect thread max-size despite being configured

Description

Riptide takes connections.max-per-route as max thread if connections.max-per-route is greater than threads.max-size.

riptide:
  defaults:
    threads:
      max-size: 15
    connections:
      time-to-live: 30 seconds
      max-per-route: 30 

Expected Behavior

Riptide should configure threads.max-size as max thread for it thread pool.

Actual Behavior

Riptide takes connections.max-per-route as max thread if connections.max-per-route is greater than threads.max-size.

Possible Fix

Not include connections.max-per-route in deciding what would be max thread when merging defaults. If no max-thread is configured, then it should take default max thread as max thread

https://github.com/zalando/riptide/blob/main/riptide-spring-boot-autoconfigure/src/main/java/org/zalando/riptide/autoconfigure/Defaulting.java#L105

Steps to Reproduce

1. Configure your riptide to have connections.max-per-route is greater than threads.max-size

Context

Your Environment

• Version used: 4.0.0