[Blazor] Serialization optimizations

[javiercn]

There are many places on the stack where we serialize payloads multiple times to/from strings.

• JSInterop
• Root component markers
• Persistent component state

While there are no functional issues with the current approach and performance is acceptable. There is an opportunity for us to reduce memory usage and improve performance on some of these APIs that get called regularly.

We know for a fact that in some cases it has a clear impact, for example in JS interop.