blhc and debdiff tasks are constrained to run on workers of the same architecture

blhc and debdiff tasks are tied to the architecture of the data that they're analyzing. But this isn't technically required. Both blhc and debdiff can operate on foreign architectures without any penalty.

We think this was done to allow environment lookups to happen early. However, environment lookups are done again in the final task configuration, after worker assignment, so this shouldn't actually be required.

Can anyone think of a reason that we can't remove host_architecture from these tasks?