Attempt to further split explicit template instantiations into separate files

[msimberg]

e.g. by element type. One benefit would be to expose more parallelism in the build. A potential downside is even higher memory consumption during builds (which might anyway limit the parallelism).

[msimberg]

Are we still interested in doing this? Might be nice, but it's unclear if there's a benefit. I'd close and if it seems like a good idea in the future we'll for sure rediscover this?