ci: drop the docker layer cache and stop installing unused tooling (#5544)

Two cleanups, neither changing what is built or published.

docker.yml loses its type=gha layer cache. The image build compiles nothing —
it downloads a release zip and runs apk/apt — so the cache could only save the
minute or two those take, against a real correctness problem: with
RELEASE=latest the binary URL is resolved by curl inside a RUN layer, and the
layer key does not include what it resolved to. A rebuild at the same RELEASE
value (a dispatch with version=latest, or a re-run of the same version) would
hit the old layer and ship the previous release's binary. mode=max also drew on
the same repo-wide 10GB Actions cache quota the Rust lanes are contending for.

Only RELEASE is passed as a build-arg now; it is the sole one the Dockerfiles
declare besides TARGETARCH. BUILDTIME, VERSION, BUILD_TYPE, REVISION and CHANNEL
were read by no stage, and BUILDTIME's $(date ...) was a literal string in the
YAML block rather than a substitution. The DOCKER_CHANNEL computation that fed
CHANNEL evaluated to "release" down every branch and is gone with it. BUILD_DATE
and VCS_REF stay unset even though the Dockerfiles declare them: supplying them
would change the published image labels.

The setup composite stops installing tools its callers do not use. protobuf-
compiler comes out of the apt list entirely — setup-protoc installs 34.1 into
the tool cache and prepends it to PATH, so the apt build was shadowed on every
run and never used; the same duplicate install is removed from the io_uring lane.
musl-tools, zip and unzip move behind install-build-packaging-tools, off for the
CI and coverage lanes and left on for build.yml, whose native musl leg needs
musl-gcc and whose packaging steps need zip. cargo-nextest and the
rustfmt/clippy components move behind install-test-tools, off only for build.yml,
which runs no tests and no lints; coverage and the nightly replication lane keep
them because both invoke nextest.

The action's github-token input is deleted along with its 20 call sites. Its
runs block never referenced it — setup-protoc uses github.token directly — so it
was 20 places handing a token to something that ignored it.

Refs: rustfs/backlog#1598, rustfs/backlog#1600, rustfs/backlog#1603

.github/actions/setup/action.yml

@@ -40,28 +40,43 @@ inputs:
     description: "Target architecture to add"
     required: false
     default: ""
-  github-token:
-    description: "GitHub token for API access"
+  install-build-packaging-tools:
+    description: >-
+      Install musl-tools/zip/unzip, needed for musl linking and release
+      packaging. Off for CI test lanes, which use none of them.
     required: false
-    default: ""
+    default: "true"
+  install-test-tools:
+    description: >-
+      Install cargo-nextest and the rustfmt/clippy components. Off for release
+      and audit lanes, which run no tests and no lints.
+    required: false
+    default: "true"
 
 runs:
   using: "composite"
   steps:
+    # protobuf-compiler is deliberately absent: the setup-protoc step below
+    # installs 34.1 into the tool cache and prepends it to PATH, so the apt
+    # build (older, and never version-matched) was shadowed on every run and
+    # simply never used.
     - name: Install system dependencies (Ubuntu)
       if: runner.os == 'Linux'
       shell: bash
       run: |
         sudo apt-get update
         sudo apt-get install -y \
-          musl-tools \
           build-essential \
           pkg-config \
           libssl-dev \
-          ripgrep \
-          unzip \
-          zip \
-          protobuf-compiler
+          ripgrep
+
+    # musl-gcc is needed by the native musl release leg, and zip/unzip by the
+    # release packaging steps. No CI test lane touches any of them.
+    - name: Install packaging and cross-linking dependencies (Ubuntu)
+      if: runner.os == 'Linux' && inputs.install-build-packaging-tools == 'true'
+      shell: bash
+      run: sudo apt-get install -y musl-tools zip unzip
 
     - name: Install protoc
       uses: rustfs/setup-protoc@a3705324d8f9bf5b6c3573fb6cf8ae421db55dd6 # v3.0.1
@@ -79,7 +94,7 @@ runs:
       with:
         toolchain: ${{ inputs.rust-version }}
         targets: ${{ inputs.target }}
-        components: rustfmt, clippy
+        components: ${{ inputs.install-test-tools == 'true' && 'rustfmt, clippy' || '' }}
 
     - name: Install Zig
       if: inputs.install-cross-tools == 'true'
@@ -90,6 +105,7 @@ runs:
       uses: taiki-e/install-action@a21ae4029b089b9ddc45704028756f51ab8abe48 # cargo-zigbuild
 
     - name: Install cargo-nextest
+      if: inputs.install-test-tools == 'true'
       uses: taiki-e/install-action@96c7780c1d8a2b8723e12031def873a434d39d8d # nextest
 
     - name: Setup Rust cache