ci: remove artificial build throttles and fix caching gaps (#4200)

Speeds up the CI pipeline without changing what is tested:

- Drop the global CARGO_BUILD_JOBS=2 and per-job --jobs 2 flags, which
  halved compiler parallelism on the 4-core runners.
- Stop embedding hashFiles(Cargo.lock) in rust-cache shared keys. The
  action already fingerprints lockfiles internally; putting the hash in
  the key prefix meant any PR that touched Cargo.lock started from a
  completely cold cache instead of reusing unchanged dependencies.
- Give the e2e-tests job the full setup action with dependency caching.
  Its migration-proof step compiles the e2e_test crate (which pulls in
  most of the workspace) and previously did so cold on every run with
  no cache, on a 2-core runner.
- Set profile.dev debug = "line-tables-only": keeps usable backtraces
  while cutting compile/link time, target-dir size (faster cache
  save/restore), and debug-binary artifact upload/download.
- Split fmt + repo-script checks into a compile-free quick-checks job
  on ubuntu-latest so contributors get feedback in ~1 minute instead
  of after the full test run.
- Collapse the five per-filter migration-proof cargo test reruns into
  one filtered nextest invocation; the same tests already run in the
  full nextest pass.
- Remove the touch rustfs/build.rs + forced rebuild from the debug
  binary jobs (version stamping is irrelevant for e2e binaries) and
  the unreachable Windows cross-compile branch in build.yml.

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

.github/workflows/build.yml

@@ -224,7 +224,7 @@ jobs:
         with:
           rust-version: stable
           target: ${{ matrix.target }}
-          cache-shared-key: build-${{ matrix.target }}-${{ hashFiles('**/Cargo.lock') }}
+          cache-shared-key: build-${{ matrix.target }}
           github-token: ${{ secrets.GITHUB_TOKEN }}
           cache-save-if: ${{ github.ref == 'refs/heads/main' || startsWith(github.ref, 'refs/tags/') }}
           install-cross-tools: ${{ matrix.cross }}
@@ -260,14 +260,8 @@ jobs:
           touch rustfs/build.rs
 
           if [[ "${{ matrix.cross }}" == "true" ]]; then
-            if [[ "${{ matrix.platform }}" == "windows" ]]; then
-              # Use cross for Windows ARM64
-              cargo install cross --git https://github.com/cross-rs/cross
-              cross build --release --target ${{ matrix.target }} -p rustfs --bins
-            else
-              # Use zigbuild for other cross-compilation
-              cargo zigbuild --release --target ${{ matrix.target }} -p rustfs --bins
-            fi
+            # All cross targets in the matrix are Linux; zigbuild handles them.
+            cargo zigbuild --release --target ${{ matrix.target }} -p rustfs --bins
           else
             cargo build --release --target ${{ matrix.target }} -p rustfs --bins
           fi