dim: add support for applying patches using b4
Add 'shazam-branch' subcommand to apply a patch series using b4 [1], fetching the patches from Lore. You can either specify the series using message-id on the command-line, or by piping a message in the series to the subcommand. Additional b4 command-line options may be specified as needed, for example to apply individual patches.
b4 is a much more robust alternative to pretty much everything we do in dim_apply_branch() and apply_patch() functions, and automatically gathers reviews and acks from the list.
[1] https://b4.docs.kernel.org/en/latest/index.html
Okay, so I have 0 experience with b4, but a lot of experience in dim, and I think we need to start phasing out pretty much all the homebrew bash code related to applying patches, and replace with b4.
Thoughts?