support exclude default-filters by route specific

Example:

spring:
  cloud:
    gateway:
      default-filters:
      - StripPrefix=1
      routes:
      - id: example-service
        uri: lb://example-service
        predicates: 
        - Path=/example-service/**

some routes do not require a default filter...

can add the excludeDefaultFilters attribute to support it, such as:

spring:
  cloud:
    gateway:
      default-filters:
      - StripPrefix=1
      routes:
      - id: example-service
        uri: lb://example-service
        predicates: 
        - Path=/example-service/**
        exclude-default-filters: StripPrefix

The issue names no files or tests; start by tracing how spring.cloud.gateway default-filters are applied to configured routes. Compare the requested exclude-default-filters route syntax with the existing route and filter handling, and consider the work done when one route can omit a named default filter while other routes still receive it.