[Pre3] Boot config file name change (`blazor.boot.json` 👉 `dotnet.boot.js`)

[guardrex]

#35057 (comment)

[maraf]

There is still possibility of merging the config file completely into the dotnet.js (one of the underlaying scripts behind blazor.web(assembly).js

[guardrex]

I see ... so should this be held off until Preview 4?