Share implementations for Flutter `Builder`-like assists

[bkonyi]

Builder, FutureBuilder, StreamBuilder, ValueListenableBuilder, etc. "wrap with" assists all have similar implementations that could be mostly shared. We should consider refactoring them in a similar fashion to the FlutterWrap assists.

[FMorschel]

I volunteer for this. Edit: waiting on #60071 CL to land.

[FMorschel]

To mention, this is also somewhat related to flutter/flutter-intellij#4540. Once I close this, I'll open a new issue for questioning the team on other builders they mentioned there like AnimatedBuilder and LayoutBuilder, so we can answer and maybe close that issue too (either by implementing or by deciding this is enough).

[FMorschel]

I see no assist to wrap with StreamBuilder on another StreamBuilder. I see why you would do that on another Builder but you can have more than one stream to listen to. This was not followed on #60071 for ValueListenableBuilder. Since I'm here already, should I do the test on Builder only?

WDYT @pq ?

[FMorschel]

Here is the CL. I did what I suggested above, if needed I can revert https://dart-review.googlesource.com/c/sdk/+/408860.

[bwilkerson]

See also https://dart-review.googlesource.com/c/sdk/+/408341.

@kenzieschmoll For the StreamBuilder question.

[FMorschel]

Her answer on the CL:

Great. Allowing multiple wraps of same type for StreamBuilder and ValueListenableBuilder sounds good to me.

[FMorschel]

Only waiting on #34364 's CL (https://dart-review.googlesource.com/c/sdk/+/408341) to land for me to continue this change.

[FMorschel]

Can I get a new review here please @bwilkerson? Thanks a lot! I'm still waiting on a position about the parameter type discussion there.