Closes gh-16346

Closes gh-16345

Closes gh-16359

Closes gh-16358

See gh-16400

Closes gh-16400

Closes gh-16339

Closes gh-16338

In addition to upgrading to Jetty 9.4.15, this commit updates the
KeyStores used in embedded container testing to add to their entries
subject alternative name extensions for localhost and 127.0.0.1. As
of 9.4.16, Jetty requires the SAN extensions.

Closes gh-16188

Closes gh-16372

Closes gh-16387

Closes gh-16378

Closes gh-16377

Closes gh-16376

Closes gh-16375

Closes gh-16374

Closes gh-16373

Closes gh-16371

Closes gh-16370

Closes gh-16369

Previously, if the directory to which Tomcat would write a file upload did not exist
the upload attempt would fail and a 500 response would be returned to the client.
This could happen when, for example, Tomcat is using a temporary directory for file
uploads and tmpwatch has deleted the directory.

This commit configures Tomcat so that, during multipart request parsing, it will
automatically create the directory to which the parts will be written if it does not
already exist.

Closes gh-9616

Closes gh-16364

Closes gh-16363

Closes gh-16362

Closes gh-16361

* gh-16319:
  Polish "Use HTTPS for external links wherever possible"
  Use HTTPS for external links wherever possible

See gh-16319