Auto merge of #3270 - JohnTitor:crate-deps-cleanup, r=jtgeibel

Update some crates to reduce deps

This updates only the crates that reduce/replace their dependencies. Each commit has the `cargo update` log.

## Removed
- bytes v0.5.6
- generator v0.6.23
- loom v0.3.6
- scoped-tls v1.0.0
- maybe-uninit v2.0.0

## Replaced
- smallvec v0.6.13 -> tinyvec v1.1.1

r? `@jtgeibel`

Author: bors