maketest.sh: Add process cleanup for Windows at the end of testing

[sxa]

Hopefully fixes adoptium/infrastructure#1573 by checking for, and attempting to stop, java processes on the machine that have been created since the time that the test job was started. This should prevent process leaks across jobs which cause a number of failures either of failed tests or locked directories that cannot be cleaned up. Equivalent functionality may well be moved into TKG at a later point.

Draft until I've verified that the functionaliy doesn't cause any new breaks

As per adoptium/infrastructure#1669 (comment) and #2058 (comment)

Signed-off-by: Stewart X Addison sxa@redhat.com

[sxa]

FYI @Willsparker :-)

[smlambert]

Grinders: 4834, 4835, and 4838 plus PR github workflows pass (with one unrelated exception on jdk15, as expected, since this code is only invoked if on Jenkins / EXECUTOR_NUMBER defined).

[smlambert]

Some very minor comments, overall LGTM, will await Grinders to complete (and if you wanted to update echo statements/comments or not) before merging.