Prior to this commit, `DispatcherServlet` would completely reset the
response (status, headers and body) before handling errors within Spring
MVC. This can cause unintended consequences when Servlet Filters added
response headers before the error happened. Such response headers might
be still required in case of error handling.
This commit changes the complete reset of the response to only resetting
the response buffer, if possible.
Closes gh-31154
See gh-31104
0f945873a3