Always include "bench" label in benchmark workflow runners and use machine-specific cache keys

[Copilot]

Adjusts the benchmark workflows to ensure benchmarks only run on benchmark-capable runners and use machine-specific caching.

Changes Made

• Runner Labels: Modified runner label building to always include "bench" alongside "self-hosted" (similar to how "self-hosted" was already always included). The runner_labels input now only accepts additional labels beyond the required ones.
• Cache Keys: Changed cache keys from inputs.runner_labels to runner.name to ensure machine-specific caching, since different machines may have different performance characteristics.
• Bug Fix: Corrected pre-existing typos where inputs.runner_label (singular) was used instead of inputs.runner_labels (plural) in 6 places across both workflow files.

These changes are made in both bench-mpmc.yml and bench-spsc.yml workflow files.

Validation

• ✅ actionlint passes with no issues
• ✅ Code review passed
• ✅ Security scanning shows no alerts

Original prompt

adjust the benchmark workflows to add the "bench" label to selected runners by default. we only want to run the benchmark workflows on benchmark capable runners.

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[richkcho]

@copilot please review and fix the reviewdog comments on the PR.

[Copilot]

@copilot please review and fix the reviewdog comments on the PR.

Fixed the actionlint issues in commit e664c3b. The problems were pre-existing typos: inputs.runner_label (singular) should have been inputs.runner_labels (plural) in 6 places across both workflow files (cache keys and shared-key configurations).

[richkcho]

stamp pls

[richkcho]

Let's change this to have bench be a label that will always be included, like "self-hosted". Also, the key for caching should be something unique to the machine, since machines may have different characteristics.

[richkcho]

Let's change this to have bench be a label that will always be included, like "self-hosted". Also, the key for caching should be something unique to the machine, since machines may have different characteristics.
@copilot please take a look

[Copilot]

Let's change this to have bench be a label that will always be included, like "self-hosted". Also, the key for caching should be something unique to the machine, since machines may have different ch...

Done in commit bea001c. The "bench" label is now always included in runner selection (like "self-hosted"), and cache keys now use runner.name for machine-specific caching.