WIP: pigweed on veer

[cfrantz]

This is a early port of the pigweed kernel and some of its test programs to the VeeR core present in caliptra-mcu.

1. I'm creating a "devbundle" from the caliptra repos to avoid having to make bazel interact with a (IMHO) very customized cargo+xtask configuration in calipta-mcu. Some time should be spent seeing if bazel can work with the caliptra repos. The binaries in the devbundle were built from my fork where I added the dev-bundle xtask. I am not a caliptra expert and make no claims that I'm doing things "the right way" in my fork.
2. The IPC test program isn't working. I haven't yet investigated why.