The `TraceLogger` implementation is deprecated and this PR removes it
completely.

Unresolved: there is an example in `tracing-macros`, "factorial", that uses
`TraceLogger` as an example of the `tracing_macros::dbg`. The macro itself seems
broken though, so not sure if it needs to be fixed.

…gger

* upstream/master: (31 commits)
  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)
  docs: switch to intra-doc links in tracing-core (tokio-rs#1010)
  tracing-opentelemetry: implement additional record types (bool, i64, u64) (tokio-rs#1007)
  core: add intrusive linked list for callsite registry (tokio-rs#988)
  ...