As an alternative to tokio-rs#1045, this PR switches `set_default` and `with_default` to take an owned `Dispatch` instead of a ref.

See [comment here](tokio-rs#1045 (comment)) for motivation.

Closes tokio-rs#455
Part of tokio-rs#922

…spatch-as-owned-tokio-rs#455

* upstream/master: (34 commits)
  subscriber: remove TraceLogger (tokio-rs#1052)
  subscriber: make Registry::enter/exit much faster (tokio-rs#1058)
  chore(deps): update env_logger requirement from 0.7 to 0.8 (tokio-rs#1050)
  chore: fix tracing-macros::dbg (tokio-rs#1054)
  chore(deps): update pin-project requirement from 0.4 to 1.0 (tokio-rs#1038)
  chore: remove duplicated section from tracing/README.md (tokio-rs#1046)
  opentelemetry: prepare for 0.8.0 release (tokio-rs#1036)
  docs: add favicon for extra pretty docs (tokio-rs#1033)
  subscriber: fix `reload` ergonomics (tokio-rs#1035)
  chore(deps): update crossbeam-channel requirement from 0.4.2 to 0.5.0 (tokio-rs#1031)
  opentelemetry: Assign default ids if missing (tokio-rs#1027)
  chore: remove deprecated add-path from CI (tokio-rs#1026)
  attributes:  fix `#[instrument(err)]` in case of early returns (tokio-rs#1006)
  core: remove mandatory liballoc dependency with no-std (tokio-rs#1017)
  chore(deps): update cfg-if requirement from 0.1.10 to 1.0.0 (tokio-rs#1023)
  subscriber: warn if trying to enable a statically disabled level (tokio-rs#990)
  subscriber: use macros for module declarations (tokio-rs#1009)
  chore: remove `stdlib.rs` (tokio-rs#1008)
  core: fix linked list tests reusing `Registration`s (tokio-rs#1016)
  subscriber: support dash in target names (tokio-rs#1012)
  ...

…spatch-as-owned-tokio-rs#455

* upstream/master:
  subscriber: update sharded-slab to 0.1, pool hashmap allocations (tokio-rs#1062)
  subscriber: remove deprecated type, structs, and methods tokio-rs#1030
  core: rename Subscriber to Collect (tokio-rs#1015)
  chore: fix rustdoc warning in tracing-subscriber (tokio-rs#1061)

…spatch-as-owned-tokio-rs#455

…nt to clone the Dispatch