Remove Goose load tests

[lucarlig]

Summary

• remove the Goose-based contextforge-load-test workspace crate and saved performance report
• prune Goose-only dependencies and the obsolete cargo-deny advisory exception
• document the control-plane Locust suite through cf-integration as the performance-testing path

Verification

• cargo fmt --all --check
• cargo clippy --locked --workspace --all-targets -- -D warnings
• cargo nextest run --locked --workspace (209 passed, 11 skipped)
• cargo deny check advisories licenses
• cargo build --locked --workspace
• cargo shear --check-test-targets --deny-warnings --locked
• mdbook build _context/wiki
• mdbook test _context/wiki