OpenTelemetry.Internal.SelfDiagnosticsFileSink
Writes self-diagnostics entries to a rolling log file. This sink is purely the rolling-file
concern - naming, preamble/header emission, size-based rollover, retention pruning, and
failure recovery. Queueing and threading live in SelfDiagnosticsSinkDispatcher,
which invokes Write and Flush from a single pump thread.