feat(request-id): add UUID v7 support via algorithm uuidv7

[shreemaan-abhishek]

Summary

• Adds UUID v7 (RFC 9562) generation support to the request-id plugin via algorithm: "uuidv7"
• UUID v7 provides time-ordered, lexicographically sortable IDs with millisecond precision
• Includes worker-local monotonic sequence to guarantee uniqueness and ordering within a single millisecond

Test plan

• Schema validation tests (valid/invalid algorithm values)
• Format validation (version nibble = 7, variant = 8-b)
• Uniqueness test (180 concurrent requests)
• Monotonicity test (sequential UUIDs are lexicographically ordered)
• Timestamp encoding test (48-bit ts non-zero, no LuaJIT truncation)
• Custom header name support
• Sequence overflow handling
• Clock rollback resilience