feat(batch42): implement foundation helpers — msgtrace, monitor helpers, scheduler
Group A: Create MsgTrace.cs with TraceCompressionType, MsgTraceState (factory
methods, pipeline event helpers, sendEvent/sendEventFromJetStream, trace header
injection) and MsgTraceHelper (sample, genHeaderMapIfTraceHeadersPresent,
initAndSendIngressErrEvent, isMsgTraceEnabled, msgTraceSupport). Adds Trace field
to PublishArgument and Trace accessor to ParseContext.
Group C: Create MonitorHelpers.cs with GatewayzOptions, Gatewayz, RemoteGatewayz,
AccountGatewayz, ExtImport, ExtServiceLatency types; plus 25 standalone helper
functions (newSubsDetailList, newSubsList, createProxyInfo, makePeerCerts,
decodeBool, decodeUint64, decodeInt, decodeState, decodeSubs, newSubDetail,
newClientSubDetail, myUptime, tlsCertNotAfter, urlsToStrings, getPinnedCertsAsSlice,
getMonitorGWOptions, createOutboundRemoteGatewayz, createOutboundAccountsGatewayz,
createAccountOutboundGatewayz, createInboundAccountsGatewayz,
createInboundAccountGatewayz, ResponseHandler, handleResponse, newExtServiceLatency,
newExtImport).
Group D: Implement GetScheduledMessages in MsgScheduling; add Seq field to InMsg
for out-of-band scheduling sort. Group B (GatewayInterestMode.String) already complete.
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