fix(ls): include version summaries in JSON output

[overtrue]

Related issue(s)

This change comes from the test-gap detection sweep for recent ls --versions work.

Background

The recent ls --versions implementation added JSON pagination metadata and text-mode summaries, but --summarize still had no effect when the command was used with --json.

For users relying on structured output, that meant the new version-listing path behaved differently from the existing ls --json --summarize object-listing paths, which already expose totals in the response body.

Root cause

The JSON formatter for ls --versions only serialized items, truncated, and pagination markers. It ignored the summarize flag entirely even though the command already computed the same totals for text output.

Solution

The command now includes a version-specific summary block in ls --versions --json --summarize, with total version count and aggregate size. The change stays inside the recent version-listing code path and does not widen behavior outside ls --versions.

The regression coverage adds:

• a unit test for the JSON formatter summary path
• an integration test that exercises ls --versions --json --summarize against a versioned object with multiple versions

Validation

• cargo test -p rustfs-cli ls::tests --lib
• cargo test --features integration --test integration version_operations::test_ls_versions_json_summary_reports_totals
• make pre-commit