GC: Enable DATAS by default

[mangod9]

We have added a new GC mode as discussed here. We are thinking about enabling it by default with SVR GC for the next preview to gather some feedback on the feature, functionality and hoping it shows performance benefits from memory utilization standpoint.

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[mangod9]

With this change memory utilization should be significantly better, but there is a possibility of p99 latency regressions for high throughput scenarios. If you notice any throughput issues, please let us know (might need to collect GCCollectOnly profile so we could diagnose)

[mangod9]

To disable this new config, please set: DOTNET_GCDynamicAdaptationMode=0