Add caching for workload resolution, and enable by default

[dsplaisted]

#13782 adds workload resolution, but puts it behind a feature flag which is off by default. It also doesn't cache resolver results, so will likely impact perf on large solutions (especially in VS).

We should:

• Add the caching
• Enable the workload resolution by default.
• Update the error message when a workload isn't installed to suggest which workloads to install (instead of just telling you which workload packs are missing). That depends on Implement workload suggestion API #13719
• Enable the workload tests on Full Framework MSBuild. They were passing locally but not in CI. Also related: Adding end to end test coverage for global.json SDK resolution #13211
• Update OverlaySdkOnLKG.targets to calculate version band for test manifests