`cargo dev bless` doesn't work

[Y-Nak]

cargo dev bless command seems not to work since the version of compiletest-rs is updated in #6743.

I think this is because the updated compiletest joins stage_id to output file names like zero_div_zero.stage-id.stderr, while bless.rs doesn't take it into account. (I don't know why the former version of compiletest doesn't join it although the codes related to file names seem unchanged).

I suppose we could explicitly specify config.stage_id = "" in here as a quickfix.

ref: #5394

[camsteffen]

We may want to just migrate to the bless feature that is now available in compiletest itself.

[Y-Nak]

Yeah, it's most desirable, but I suppose it's worth doing a quick-fix since it seems the transition to new bless needs more discussion.