dillon1000/react

[Flight] Rename Chunk constructor to ReactPromise (#30747)

When printing these in DevTools they show up as the name of the
constructor so then you pass a Promise to the client it logs as "Chunk"
which is confusing.

Ideally we'd probably just name this Promise but 1) there's a slight
difference in the .then method atm 2) it's a bit tricky to name a
variable and get it from the global in the same scope. Closure compiler
doesn't let us just name a function because it removes it and just uses
the variable name.