CI: Run tests and clippy lints against 1.64.0

criterion 0.4 now has an MSRV of 1.59 due to its dependencies, and pprof
has an MSRV of 1.64 due to its dependencies. This is a follow-on to
0c53a91.

.github/workflows/ci.yml

@@ -36,7 +36,7 @@ jobs:
       - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.57.0
+          toolchain: 1.64.0
           override: true
       - name: Run tests
         uses: actions-rs/cargo@v1
@@ -45,20 +45,20 @@ jobs:
           args: --verbose
 
   clippy-test:
-    name: Clippy (1.57.0)
+    name: Clippy (1.64.0)
     timeout-minutes: 30
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
       - uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.57.0
+          toolchain: 1.64.0
           components: clippy
           override: true
       - name: Run clippy
         uses: actions-rs/clippy-check@v1
         with:
-          name: Clippy (1.57.0)
+          name: Clippy (1.64.0)
           token: ${{ secrets.GITHUB_TOKEN }}
           args: --all-features --all-targets -- -D warnings