Add support for signposting with OSLogs created by MetricKit

[SwiftNativeDeveloper]

Allow instrumentation to use MetricKit created OSLog instances. This will allow any signposts data to be emitted into MetricKit payloads
https://developer.apple.com/documentation/metrickit/mxmetricmanager/makeloghandle(category:)

Signposts will be created as metrics here:
https://developer.apple.com/documentation/metrickit/mxsignpostmetric

And if there is a diagnostic captured within the interval of the payload, signposts will be correlated against issues here:
https://developer.apple.com/documentation/metrickit/mxdiagnostic/signpostdata

[bryce-b]

Have you taken a look at https://github.com/open-telemetry/opentelemetry-swift/tree/main/Sources/Bridges/OTelSwiftLog ?
Does this satisfy your needs? If not, we can expand it.