Split up irods_core_builder images based on branch/standard library implementation

[alanking]

Our irods_core_builder images currently install all of the irods-externals packages. We now have -libcxx versions of many of these packages in addition to the long history of externals which may exist on some platforms which have been around for a long time.

It may be beneficial to make more purpose-specific builders to reduce image sizes and build times.

On the other hand, having builders with all of the externals available may in the end save space over having many purpose-specific builders.