Respond to comments and start adding tests

Fix re-exports and extern-crate

Add expected output tests

Add restricted paths

Format

Fix: associated methods missing in output

Ignore stripped items

Mark stripped items

removing them creates dangling references

Fix tests and update conversions

Don't panic if JSON backend fails to create a file

Fix attribute error in JSON testsuite

Move rustdoc-json to rustdoc/

This way it doesn't have to build rustc twice. Eventually it should
probably get its own suite, like rustdoc-js, but that can be fixed in a
follow-up.

Small cleanups

Don't prettify json before printing

This fully halves the size of the emitted JSON.

Add comments

[BREAKING CHANGE] rename version -> crate_version

[BREAKING CHANGE] rename source -> span

Use exhaustive matches

Don't qualify imports for DefId

Rename clean::{ItemEnum -> ItemKind}, clean::Item::{inner -> kind}

Fix Visibility conversion

clean::Visability was changed here:
https://github.com/rust-lang/rust/pull/77820/files#diff-df9f90aae0b7769e1eb6ea6f1d73c1c3f649e1ac48a20e169662a8930eb427beL1467-R1509

More churn catchup

Format

Move rustdoc/rustdoc-json to rustdoc-json

Scaffold rustdoc-json test mode

Implement run_rustdoc_json_test

Fix up python

Make tidy happy

Go back to CRATE_DEF_INDEX

Minor niceness improvements

Don't output hidden items

Remove striped items from fields

Add $TEST_BASE_DIR

Small catch