Describe the issue or suggestion

When creating a metric directly from the meter (i.e. meter.CreateCounter) you have the ability to set the unit type of the metric. When using the attributes to source gen a strongly typed metric it doesn't seem to be possible at this time to set the unit of those types of metrics.

For example:
Existing declaration:
[Histogram<long>(typeof(MetricTags))] public static partial Latency CreateLatency(Meter meter);

New declaration:
[Histogram<long>(typeof(MetricTags), unit: "ms")] public static partial Latency CreateLatency(Meter meter);

Document Details

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• ID: c021bbda-73b0-06ba-86c4-6c63fc0cc077
• Version Independent ID: bb734404-245e-8267-b271-f195a3b116c8
• Platform ID: b763bf64-71dc-d17c-c0c6-a21ab7114c45
• Content: Compile-time metric source generation - .NET
• Content Source: docs/core/diagnostics/metrics-generator.md
• Service: dotnet-fundamentals
• GitHub Login: @tommcdon
• Microsoft Alias: tommcdon