Allow Routed Aliases to use Collection Properties instead of core properties

The current routed alias code is relying on a core property named routedAliasName to detect when the Routed Alias wrapper URP should be applied to Distributed Update Request Processor. 

#Written by CorePropertiesLocator
#Sun Mar 03 06:21:14 UTC 2019
routedAliasName=testalias21
numShards=2
collection.configName=_default
... etc...

Core properties are not changeable after the core is created, and they are written to the file system for every core. To support a unit test for SOLR-13419 I need to create some legacy formatted collection names, and arrange them into a TRA, but this is impossible due to the fact that I can't change the core property from the test. There's a TODO dating back to the original TRA implementation in the routed alias code to switch to collection properties instead, so this ticket will address that TODO to support the test required for SOLR-13419.

Back compatibility with legacy core based TRA's and CRA's will of course be maintained. I also expect that this will facilitate some more nimble handling or routed aliases with future auto-scaling capabilities such as possibly detaching and archiving collections to cheaper, slower machines rather than deleting them. (presently such a collection would still attempt to use the routed alias if it received an update even if it were no longer in the list of collections for the alias)