add comments in `store_dead_field_or_variant`
support multiple log level
add a item ident label
fix ui tests
fix a ui test
fix a rustdoc ui test
use let chain
refactor: remove `store_dead_field_or_variant`
fix a tiny bug
This can be replicated in full with other existing features, there's no
need to have a separate option for it.
This also fixes a bug where `--test-args=--show-output` had no effect,
and updates the documentation.
