JBIDE-16122 maint

[robstryker]

Initialization of Download Runtimes wizard is not cancelable.

[fbricon]

you should point at the recommended method call, even if it's obvious here. Same remarks for the rest of deprecated methods

[fbricon]

Something's wrong in the stacks retrieval logic. So let's say github is down, we fail at d/l-ing the file, since the stacks client uses the same url, we also skip it : then nothing is returned. BUT the client stacks embeds a stacks yaml so it would need to be returned instead. In order to do that without opening the stacks client jar, we can use something like

StacksClientConfiguration config = new DefaultStacksClientConfiguration();
config.setOnline(false);
StacksClient client = new StacksClient(config, new JBTStacksMessages());

[fbricon]

looks fine. +1 after commits are squashed