Add exclude list to addon dedupe logic

[nlfurniss]

The following is cobbled together from a JIRA ticket, so it is a bit fragmented.

Summary

When addons try to access ember-cli-babel during the build stage, EMBER_ENGINES_ADDON_DEDUPE=true can cause this.addons to be empty. Instead of requiring addons to do something like this.addons.find(...) || this.project.addons.find(...), we should exclude ember-cli-babel from dedupe logic so it's available.

Related code in ember-engines:

ember-engines/packages/ember-engines/lib/engine-addon.js

Line 845 in e247643

mergeTrees(this.nonDuplicatedAddonInvoke('treeFor', ['vendor']), {

ember-engines/packages/ember-engines/lib/engine-addon.js

Lines 397 to 417 in e247643

	let trees
	try {
	deeplyNonDuplicatedAddon(hostAddons, this, treeName);
	trees = this.addons
	.filter(addon => {
	if (!addon[methodName]) {
	// no method to call
	return false;
	}
	return true;
	})
	.map(addon => {
	return addon[methodName].apply(addon, invokeArguments);
	});
	} finally {
	restoreOriginalAddons(this);
	}
	return trees

cc: @rwjblue @brendenpalmer