chore(CI): split CI into separate workflows (#1723)

* chore(CI): split CI into separate workflows

Tracing runs a very large number of jobs on CI. Right now, those jobs
are all defined in a single workflow. Unfortunately, GitHub Actions only
allows restarting failed actions at the workflow level --- if a single
job fails spuriously and we want to rerun it, we currently have to
re-run *all* the jobs we run on CI. This makes rerunning a single failed
job take much longer than is generally necessary.

This branch changes the CI configuration to split each logical set of
jobs into a separate workflow. This way, if (for example) the MSRV `cargo
check` job fails spuriously, we can restart only the MSRV checks
workflow, and not have to re-run (for example) all the WASM test jobs
too.

This doesn't actually change what any of these jobs do, just moves them
into separate yaml files with separate names.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

.github/workflows/check.yml

@@ -0,0 +1,79 @@
+name: Checks
+
+on:
+  push:
+    branches:
+    - master
+  pull_request: {}
+
+env:
+  # Disable incremental compilation.
+  #
+  # Incremental compilation is useful as part of an edit-build-test-edit cycle,
+  # as it lets the compiler avoid recompiling code that hasn't changed. However,
+  # on CI, we're not making small edits; we're almost always building the entire
+  # project from scratch. Thus, incremental compilation on CI actually
+  # introduces *additional* overhead to support making future builds
+  # faster...but no future builds will ever occur in any given CI environment.
+  #
+  # See https://matklad.github.io/2021/09/04/fast-rust-builds.html#ci-workflow
+  # for details.
+  CARGO_INCREMENTAL: 0
+  # Allow more retries for network requests in cargo (downloading crates) and
+  # rustup (installing toolchains). This should help to reduce flaky CI failures
+  # from transient network timeouts or other issues.
+  CARGO_NET_RETRY: 10
+  RUSTUP_MAX_RETRIES: 10
+  # Don't emit giant backtraces in the CI logs.
+  RUST_BACKTRACE: short
+
+jobs:
+  check:
+    # Run `cargo check` first to ensure that the pushed code at least compiles.
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@main
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        profile: minimal
+        override: true
+    - name: Check
+      uses: actions-rs/cargo@v1
+      with:
+        command: check
+        args: --all --tests --benches
+
+  style:
+    # Check style.
+    needs: check
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@main
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        components: rustfmt
+        profile: minimal
+        override: true
+    - name: rustfmt
+      uses: actions-rs/cargo@v1
+      with:
+        command: fmt
+        args: --all -- --check
+
+  warnings:
+    # Check for any warnings. This is informational and thus is allowed to fail.
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@main
+    - uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        components: clippy
+        profile: minimal
+    - name: Clippy
+      uses: actions-rs/clippy-check@v1
+      with:
+        token: ${{ secrets.GITHUB_TOKEN }}
+        args: --all --examples --tests --benches -- -D warnings