Change how security advisories work on CI (#3461)

Before this commit we actually have two builders checking for security
advisories on CI, one is `cargo audit` and one is `cargo deny`. The
`cargo deny` builder is slightly different in that it checks a few other
things about our dependency tree such as licenses, duplicates, etc. This
commit removes the advisory check from `cargo deny` on CI and then moves
the `cargo audit` check to a separate workflow.

The `cargo audit` check will now run nightly and will open an issue on
the Wasmtime repository when an advisory is found. This should help make
it such that our CI is never broken by the publication of an advisory
but we're still promptly notified whenever an advisory is made. I've
updated the release process notes to indicate that the open issues
should be double-checked to ensure that there are no open advisories
that we need to take care of.

.github/workflows/cargo-audit.yml

@@ -0,0 +1,12 @@
+name: Run cargo-audit
+on:
+  schedule:
+    - cron: '0 0 * * *'
+jobs:
+  security_audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/audit-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/main.yml

@@ -47,7 +47,7 @@ jobs:
         curl -L https://github.com/EmbarkStudios/cargo-deny/releases/download/0.8.5/cargo-deny-0.8.5-x86_64-unknown-linux-musl.tar.gz | tar xzf -
         mv cargo-deny-*-x86_64-unknown-linux-musl/cargo-deny cargo-deny
         echo `pwd` >> $GITHUB_PATH
-    - run: cargo deny check
+    - run: cargo deny check bans licenses
 
   doc:
     name: Doc build
@@ -458,21 +458,6 @@ jobs:
         files: "dist/*"
         token: ${{ secrets.GITHUB_TOKEN }}
 
-  cargo-audit:
-    env:
-      CARGO_AUDIT_VERSION: 0.11.2
-    runs-on: ubuntu-latest
-    steps:
-    - uses: actions/checkout@v2
-    - uses: actions/cache@v1
-      with:
-        path: ${{ runner.tool_cache }}/cargo-audit
-        key: cargo-audit-bin-${{ env.CARGO_AUDIT_VERSION }}
-    - run: echo "${{ runner.tool_cache }}/cargo-audit/bin" >> $GITHUB_PATH
-    - run: |
-        cargo install --root ${{ runner.tool_cache }}/cargo-audit --version ${{ env.CARGO_AUDIT_VERSION }} cargo-audit
-        cargo audit
-
   verify-publish:
     runs-on: ubuntu-latest
     steps: