Enrich standalone activity describe output with execution details

[fretz12]

What changed?

temporal activity describe now provides fuller inspection data:

• Text output includes Namespace, ExecutionTime, and SearchAttributes.
• --output json and --output jsonl request and return activity input, outcome, heartbeat details, and last failure.

JSON/jsonl continue to return the DescribeActivityExecution response directly.

Stability

• JSON/jsonl output change was reviewed as an intentional additive schema change

Design

• This works against an OSS server

Behavior

• Results continue to go to stdout; errors and warnings continue to go to stderr
• No error-message behavior changed

Tests

• Added/updated functional coverage in SharedServerSuite
• Verified text, JSON, JSONL, raw, successful outcome, failure outcome, input, and heartbeat details