ci: cross-compile Windows Bazel clippy (#20701)

## Why

#20585 moved the Windows Bazel test job to the cross-compile path, but
the Windows Bazel clippy and verify-release-build jobs were still using
the native Windows/MSVC-host fallback. Those two jobs became the slowest
Windows PR legs, even though both are build-only signal and do not need
to execute the resulting binaries.

## What Changed

- Switches the Windows Bazel clippy job from
`--windows-msvc-host-platform` to `--windows-cross-compile`, so clippy
build actions use Linux RBE while still targeting
`x86_64-pc-windows-gnullvm`.
- Switches the Windows Bazel verify-release-build job to
`--windows-cross-compile` as well. This job only compiles
`cfg(not(debug_assertions))` Rust code under `fastbuild`, so it does not
need a native Windows build host.
- Keeps the old `--skip_incompatible_explicit_targets` behavior only for
fork/community PRs without `BUILDBUDDY_API_KEY`, where `run-bazel-ci.sh`
falls back to the local Windows MSVC-host shape.
- Adds `--windows-cross-compile` support to
`.github/scripts/run-bazel-query-ci.sh`, so target-discovery queries
select the same `ci-windows-cross` config as the subsequent build.
- Threads that option through `scripts/list-bazel-clippy-targets.sh` so
the Windows clippy job discovers targets under the same platform shape
as the subsequent clippy build.

## Verification

Local checks:

```shell
bash -n .github/scripts/run-bazel-query-ci.sh
bash -n scripts/list-bazel-clippy-targets.sh
ruby -e 'require "yaml"; YAML.load_file(".github/workflows/bazel.yml"); puts "ok"'
RUNNER_OS=Linux ./scripts/list-bazel-clippy-targets.sh | grep -c -- '-windows-cross-bin$'
RUNNER_OS=Windows ./scripts/list-bazel-clippy-targets.sh --windows-cross-compile | grep -c -- '-windows-cross-bin$'
```

The Linux target-list check reported `0` Windows-cross internal test
binaries, while the Windows cross target-list check reported `47`,
preserving the test-code clippy coverage shape from the existing Windows
job.

.github/scripts/run-bazel-query-ci.sh

@@ -6,8 +6,13 @@ set -euo pipefail
 # invocation so target-discovery queries can reuse the same Bazel server.
 
 query_args=()
+windows_cross_compile=0
 while [[ $# -gt 0 ]]; do
   case "$1" in
+    --windows-cross-compile)
+      windows_cross_compile=1
+      shift
+      ;;
     --)
       shift
       break
@@ -20,7 +25,7 @@ while [[ $# -gt 0 ]]; do
 done
 
 if [[ $# -ne 1 ]]; then
-  echo "Usage: $0 [<bazel query args>...] -- <query expression>" >&2
+  echo "Usage: $0 [--windows-cross-compile] [<bazel query args>...] -- <query expression>" >&2
   exit 1
 fi
 
@@ -32,7 +37,11 @@ case "${RUNNER_OS:-}" in
     ci_config=ci-macos
     ;;
   Windows)
-    ci_config=ci-windows
+    if [[ $windows_cross_compile -eq 1 ]]; then
+      ci_config=ci-windows-cross
+    else
+      ci_config=ci-windows
+    fi
     ;;
 esac