ApplicationContextRequestMatcher can use the wrong ApplicationContext

[philwebb]

Discovered during #17912

ApplicationContextRequestMatcher uses WebApplicationContextUtils.getRequiredWebApplicationContext(request.getServletContext()) to obtain the application context and caches the supplier. If there is a management server running on a different port, it's possible for the wrong context to be used depending on who makes the first request.

[Sauhardstark]

One way might be to stop caching the context all together and call the createContext method each time. It's safe for Tomcat at least as ApplicationContext in tomcat just fetches it from a ConcurrentHashMap attributes
Another might be to maintain a ConcurrentHashMap inside ApplicationContextRequestMatcher, same as ApplicationContext.
I have also checked UnderTow and Jetty and they both do something similar (using Maps) in ServletContextImpl and ContextHandler