bump rust nightly

[thedavidmeister]

PR summary

• pulls some core-specific commands from holonix back into core so they can be managed here
• create a core-specific fmt command to workaround thread 'main' panicked at 'bad span: .: )', src/tools/rustfmt/src/source_map.rs:52:13 rust-lang/rustfmt#3685
• uses compatible versions of upstream crates
• chases the new compiler down the rabbit hole
• fixes to app spec proc test script inconsistencies with app spec test script
• disables app spec proc test on CI until it can be handled properly (not copying another test wholesale)

testing/benchmarking notes

( if any manual testing or benchmarking was/should be done, add notes and/or screenshots here )

followups

( any new tickets/concerns that were discovered or created during this work but aren't in scope for review here )

changelog

Please check one of the following, relating to the CHANGELOG-UNRELEASED.md

• this is a code change that effects some consumer (e.g. zome developers) of holochain core so it is added to the CHANGELOG-UNRELEASED.md (linked above), with the format - summary of change [PR#1234](https://github.com/holochain/holochain-rust/pull/1234)
• this is not a code change, or doesn't effect anyone outside holochain core development

[thedavidmeister]

rust-lang/futures-rs#1453

[thedavidmeister]

rust-lang/futures-rs#1445

[thedavidmeister]

rust-lang/rustfmt#3666