Refactor v2: faster pop/reserve/retain_mut, modern Criterion benches, Miri-friendly tests + fmt in CI

.github/workflows/main.yml

@@ -44,6 +44,9 @@ jobs:
       - name: Cargo test w/ malloc_size_of
         run: cargo test --verbose --features malloc_size_of
 
+      - name: Cargo fmt
+        run: cargo --all -- --check
+
       - name: Cargo check w/o default features
         if: matrix.toolchain == 'nightly'
         run: cargo check --verbose --no-default-features
@@ -92,4 +95,3 @@ jobs:
       - name: Mark the job as unsuccessful
         run: exit 1
         if: "!success()"
-

Cargo.toml

@@ -26,7 +26,13 @@ malloc_size_of = { version = "0.1.1", optional = true, default-features = false
 
 [dev-dependencies]
 bincode = "1.0.1"
+criterion = "0.8"
 
 [package.metadata.docs.rs]
 all-features = true
 rustdoc-args = ["--cfg", "docsrs"]
+
+[[bench]]
+name = "bench"
+path = "benches/bench.rs"
+harness = false