Microsoft.Data.SqlClient.UserAgent.UserAgentInfo
Gathers driver + environment info, enforces size constraints,
and serializes into a UTF-8 JSON payload.
The spec document can be found at: https://microsoft.sharepoint-df.com/:w:/t/sqldevx/ERIWTt0zlCxLroNHyaPlKYwBI_LNSff6iy_wXZ8xX6nctQ?e=0hTJX7
Provides the UTF-8 encoded UserAgent JSON payload as a cached read-only memory buffer.
The value is computed once during process initialization and reused across all calls.
No re-encoding or recalculation occurs at access time, and the same memory is safely shared across all threads.