[Deprecation] CLI Benchmark Legacy Options (`--rand-perc`, `--threads` Alias)

[silug]

Summary

Benchmark CLI still includes deprecated options/aliases.

Evidence

• src/puppetlabs/puppetdb/cli/benchmark.clj:638 errors explicitly: --rand-perc is deprecated; use --rand-catalogs and/or --rand-facts.
• src/puppetlabs/puppetdb/cli/benchmark.clj:717 help marks --rand-perc as deprecated.
• src/puppetlabs/puppetdb/cli/benchmark.clj:743 marks --threads as deprecated alias for --senders.

Proposed OpenVoxDB 9 Change

• Remove --rand-perc option entirely.
• Remove --threads alias and keep --senders only.

Compatibility / Risk

• Low risk; benchmark CLI is niche and migration is straightforward.

Implementation Notes

• Keep CLI error/help text focused on supported flags only.
• Update docs/examples/scripts that still reference deprecated options.

Acceptance Criteria

• Deprecated benchmark flags are no longer accepted.
• Help output does not list deprecated options.
• Tests/docs updated to supported flags.

Suggested Tests

• CLI parsing tests for supported benchmark flags.
• Negative tests for removed deprecated flags.

[silug]

• --threads deprecated in d194367 (8.2.0)
• --rand-perc deprecated in 8578625 (8.5.0)