[browser][coreclr] Strip workload content #134074

We should strip content of workload to a minimum, which is the required large payload of the emscripten. The goal is to be able to version (and force update) together components that possibly may contain servicing patches.

• Runtime pack, crossgen and build targets should like in the SDK the same way as on other platforms
• Emscripten binaries and minimal targets (mostly containing location logic) should be part of the workload

We don't expect to change/bump emscripten in the servicing releases. Binary location logic thus should be very constant. Any build logic related to the emscripten invocation should be tightly coupled with the rest of the runtime pack and SDK pack by versioning it with the .NET SDK itself.

• Clean-up targets in the emscripten workload
• Remove runtime pack and SDK pack from the workload manifest
• Move build logic from workload packs to the SDK pack. We need to maintain compatibility with down level targeting
• Refactor Wasm.Build.Tests setup to not depend on runtime pack and sdk pack being part of workload manifest