Reland "Fix DraggableScrollableSheet rebuilding during drag"

[moffatman]

Relands #111010 which was reverted in #112293

---

DraggableScrollableSheet was rebuilding every time the size of the child changed, which meant every frame during a drag. Now it will only rebuild when it gets changed parameters from the parent widget.

Also inadvertent fix to an exception thrown while rebuilding DraggableScrollableSheet with a new controller.

Fixes #67219

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• All existing and new tests are passing.

[Piinks]

Thanks for re-staging this @moffatman. I am just finishing fixing the customer code, we need that to land internally first before this can be merged.

[Piinks]

LGTM! The customer is fixed, this can land now. :)