split off an AsgMessaging package from AsgTools
I had briefly discussed this with @akraszna last week, and we agreed that it may be nice if the messaging code was in its own package, so I implemented that now.
Generally trying to pursue three goals here:
- it would allow other packages that AsgTools depends on to use our standard messaging and status codes. mostly thinking of the xAOD-standalone code, but there may be others. I don't have any immediate plans for updating these packages, but I was thinking that at least for release 22 we could phase out the TReturnCode.
- the AsgTools package has actually grown fairly large, there are 34 header files in the package, not all of which are that closely related to each other.
- we could point those few developers who want a stand-alone version of their package to this package as option to still use ATLAS messaging.
I put in some backwards compatibility headers in AsgTools, we can consider phasing them out when moving to master/release 22.
I did some minor updates, but for now I'm just trying to move files around, not fix any pre-existing style issues, etc.