Build: put protections around modules to avoid overwriting by layer file scenarios

[jburke]

Now with layer files, it is possible to load a module once in a layer, but still ask for it by its specific resource name/include it in another layer. Bad things can happen if the second load of the module overwrites the first definition.

In a build, put protections around each module so that it only defines the module if it has not been defined already. The protections should be in each module resource as well as inside the layer files, xd and non-xd.

[jburke]

(In [8999]) Fixes #3240: adds guards around module code to avoid redefitions in layered build scenarios

[jburke]

(In [9000]) Fixes #3240: adds guards around module code to avoid redefitions in layered build scenarios