Speed up logging once again (#9981)

* Update `tracing`-related dependencies

* Enable `parking_lot` feature in `tracing-subscriber`

* Add an asynchronous stderr logger

* Make clippy happy

* Add an integration test for the logger

* Refactor `test_logger_filters`'s subprocess machinery into a separate function

* Use a child process instead of hooking into stderr for the test

* Add a doc comment for `MakeStderrWriter`

* Move the initialization into the `MakeStderrWriter`'s constructor

* Add an extra test case to trigger the logger's emergency flush mechanism

* Use the buffer's mutex for asynchronous flushes

* Remove vestigial `nix` dependency from one of the previous commits

substrate/Cargo.lock

@@ -4085,9 +4085,9 @@ dependencies = [
 
 [[package]]
 name = "memoffset"
-version = "0.6.1"
+version = "0.6.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "157b4208e3059a8f9e78d559edc658e13df41410cb3ae03979c83130067fdd87"
+checksum = "59accc507f1338036a0477ef61afdae33cde60840f4dfe481319ce3ad116ddf9"
 dependencies = [
  "autocfg 1.0.1",
 ]
@@ -8466,6 +8466,7 @@ dependencies = [
  "chrono",
  "criterion",
  "lazy_static",
+ "libc",
  "log 0.4.14",
  "once_cell",
  "parking_lot 0.11.1",
@@ -10635,14 +10636,15 @@ dependencies = [
 
 [[package]]
 name = "tracing-subscriber"
-version = "0.2.19"
+version = "0.2.25"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ab69019741fca4d98be3c62d2b75254528b5432233fd8a4d2739fec20278de48"
+checksum = "0e0d2eaa99c3c2e41547cfa109e910a68ea03823cccad4a0525dcbc9b01e8c71"
 dependencies = [
  "ansi_term 0.12.1",
  "chrono",
  "lazy_static",
  "matchers",
+ "parking_lot 0.11.1",
  "regex",
  "serde",
  "serde_json",