Implicitly cache SDK resolvers and SDKs cross evaluations

### Issue Description

`EvaluationContext` currently contains a caching `SdkResolverService` as a field, meaning that the scope of SDK (and SDK resolver) caching is one evaluation unless the host explicitly creates a shared `EvaluationContext`. The work being done as part of initializing the resolver service has been flagged as a perf issue (ex: [AB#1364300](https://devdiv.visualstudio.com/0bdbc590-a062-4c3f-b0f6-9383f67865ee/_workitems/edit/1364300)).

It is unsupported to be changing the relevant files when MSBuild is running so we should look into implicitly caching resolvers and possibly also the resolved SDKs cross evaluations, in a process-wide cache for example.

### Data

See [AB#1364300](https://devdiv.visualstudio.com/0bdbc590-a062-4c3f-b0f6-9383f67865ee/_workitems/edit/1364300), [AB#1364293](https://devdiv.visualstudio.com/0bdbc590-a062-4c3f-b0f6-9383f67865ee/_workitems/edit/1364293), [AB#1370076](https://devdiv.visualstudio.com/0bdbc590-a062-4c3f-b0f6-9383f67865ee/_workitems/edit/1370076).