ci: migrate Bazel setup away from archived setup-bazelisk (#19851)

## Why

All Bazel CI jobs are currently blocked in the `setup-bazelisk` step
while trying to download Bazelisk.
[`bazelbuild/setup-bazelisk`](https://github.com/bazelbuild/setup-bazelisk)
is archived, and its README now recommends migrating to
[`bazel-contrib/setup-bazel`](https://github.com/bazel-contrib/setup-bazel),
so leaving our workflows on the archived action leaves CI exposed to
exactly this sort of outage.

Because `v8-canary` now consumes the shared local `setup-bazel-ci`
action, that workflow also needs to trigger when the action changes.
Without that follow-up, Bazel bootstrap regressions specific to the V8
canary path could be skipped by the workflow path filters.

## What Changed

- Switched `.github/actions/setup-bazel-ci/action.yml` from
`bazelbuild/setup-bazelisk` to `bazel-contrib/setup-bazel`, pinned to
`0.19.0`.
- Left `bazelisk-version` unset so GitHub-hosted runners can use their
preinstalled Bazelisk instead of downloading `1.x` at job start.
- Updated `.github/workflows/rusty-v8-release.yml` and
`.github/workflows/v8-canary.yml` to use the shared `setup-bazel-ci`
action instead of referencing `setup-bazelisk` directly.
- Added `.github/actions/setup-bazel-ci/**` to the `pull_request` and
`push` path filters in `.github/workflows/v8-canary.yml` so changes to
the shared Bazel setup action still run the canary workflow.
- Kept the existing repository-cache and Windows-specific Bazel setup
logic intact.

This keeps Bazel version selection anchored by `.bazelversion` while
removing the failing dependency on the archived setup action.

## Verification

- Searched `.github/` to confirm there are no remaining `setup-bazelisk`
references.
- Parsed the updated workflow and action YAML locally with Ruby's
`YAML.load_file`.

.github/actions/setup-bazel-ci/action.yml

@@ -33,7 +33,7 @@ runs:
       run: Copy-Item (Get-Command dotslash).Source -Destination "$env:LOCALAPPDATA\Microsoft\WindowsApps\dotslash.exe"
 
     - name: Set up Bazel
-      uses: bazelbuild/setup-bazelisk@b39c379c82683a5f25d34f0d062761f62693e0b2 # v3
+      uses: bazel-contrib/setup-bazel@c5acdfb288317d0b5c0bbd7a396a3dc868bb0f86 # 0.19.0
 
     - name: Configure Bazel repository cache
       id: configure_bazel_repository_cache