Motivation:

`RoutingResult.path()` should return a mapped path by `Route`.
Let's say a service which routes to `/users/{userId}` is prefixed
with `/api/v1`. If a request path is `/api/v1/users/1234`,
- `ServiceRequestContext.path()` is equal to `/api/v1/users/1234`
- `ServiceRequestContext.mappedPath()` should be equal to `/users/1234`

Before #4086, a prefixed path is internally mapped with
`PrefixPathMapping`. So a prefix path is correctly stripped.
https://github.com/line/armeria/blob/d336d8981f03001f5a12ecae3363e98b698bb08b/core/src/main/java/com/linecorp/armeria/server/PrefixPathMapping.java#L67
\#4086 introduced `Route.withPrefix()` and all `PathMapping`s are able
to be prefixed. Consequently, other `PathMapping` implementations such
as `ExactPathMapping`, should remove the prefix when building
`RoutingResult.path()`.

Modifications:

- Remove the prefix of a request path when a `RoutingContext` is applied
  to:
  - `ExactPathMapping`
  - `GlobPathMapping`,
  - `ParameterizedPathMapping`
  - `RegexPathMappingWithPrefix`

Result:

Fix a regression introduced by #4086