CFE: Correct inference of Future.value type, without a context type

[srawlins]

Implementation issue for CFE for dart-lang/language#3304.

See this code:

Object? f(int? x) { return Future.value(x)..foo; }

void main() {
  print(f(null));
}

CFE infers the type of Future.value(...) to be a Future<int?>("Error: The getter 'foo' isn't defined for the class 'Future<int?>'."). Analyzer infers it to be Future<int>. In dart-lang/language#3304, it was decided that CFE infers the wrong type here.

This discrepancy is blocking #53253.