Fix job names so they can be selected as required statuses

[masklinn]

Usually there are not many jobs and they don't overlap so their naming is easy. In this case I forgot that statuses are per-job not per file or anything, so

• the naming overlap between the "normal" python tests and the release made knowing which was which much harder than necessary
• the rust and python checks literally having the same job name made one of them (not sure which) impossible to select
• having all the rust stuff as a single "checks" jobs didn't help either, split it into checks and tests to more or less mirror the python stuff
• prefix jobs with their language as it's not out the question that the repository would grow e.g. JS bindings in neon, or a C API for FFI, or whatever, and those would need to be clearly identified