[browser][coreCLR] native trimming

- [ ] drop server GC
- [ ] drop most of the built in marshalling support. OleVariant is one of the details that makes no sense at all in wasm, but there are lots of little functions that do marshalling. Our primary scenario for marshaling these days is to use LibraryImport, which is more easily trimmed, and doesn't carry anywhere near as much baggage as built in marshalling.
- [ ] drop ICorProfiler (https://github.com/dotnet/runtime/pull/126487)
- [ ] NativeLibrary
- [ ] drop read/write metadata - details @davidwrighton
- remove what's not used by the reflection emit implementation
- change implementation of Reflection.Emit to use managed reflection emit
- alternative approach based on dnmd
- `CMiniMdRW::SaveToStorage`, `CMiniMdRW::PreSaveFull` - "I don't think we need to actually save it"
- [ ] built-in marshalling
- [ ] [BACKGROUND_GC](https://github.com/dotnet/runtime/blob/0a726991ba412269ae8bb54ed3aa829466e0d0c8/src/coreclr/gc/gcpriv.h#L193)