integration tests should share runtime downloads so that each test doesn't have to re-download the same runtime zips, and no longer use EOL'd runtimes

While running the integration tests today to investigate JBDS-4077, I discovered that:

• org.jboss.ide.eclipse.as.ui.bot.test requires 11 runtimes, some of which are well past their EOL date [1]:

  jboss-3.2.8.SP1  jboss-4.2.3.GA  jboss-5.1.0.GA     jboss-as-7.0.2.Final  wildfly-10.0.0.CR2   wildfly-9.0.1.Final
  jboss-4.0.5.GA   jboss-5.0.1.GA  jboss-6.1.0.Final  jboss-as-7.1.1.Final  wildfly-8.2.0.Final

• org.jboss.tools.deltaspike.ui.bot.test requires 1 runtime, wildfly-10.0.0.Final

[1] https://access.redhat.com/support/policy/updates/jboss_notes/eol vs. https://access.redhat.com/support/policy/updates/jboss_notes/

So, three problems here:

a) different tests use different versions of the same runtime (WFLY 10.0.0.CR2 vs. Final)
b) different tests re-download their runtimes every time you do a clean, instead of fetching runtimes from a cache. So the same 160M of WFLY 10 gets downloaded twice.
c) we still test on runtimes that have been EOL'd years ago, such as AS 4.0 and earlier.