Review the need for TomcatAccess, JettyAccess, and UndertowAccess

[wilkinsona]

They're test classes used to provide public access to otherwise package-private methods. It would be good to review the code and see if we can remove the need for them as part of the restructuring efforts. TomcatAccess is somewhat related to #44325 as it may be addressed by having servlet- and reactive-specific TomcatWebServer sub-classes.