* Revert "Roll Dart SDK from 094c9024373c to 2ea89ef8f6de (1 revision) (#26030)"

This reverts commit 0d62a560.

* Revert "Roll Dart SDK from 04e55dad908d to 094c9024373c (1 revision) (#26027)"

This reverts commit 06cbf1e0.

* Revert "Roll Dart SDK from b4210cc43086 to 04e55dad908d (2 revisions) (#26020)"

This reverts commit d1a11828.

* Revert "Roll Dart SDK from 86c749398b3a to b4210cc43086 (2 revisions) (#26006)"

This reverts commit 3ffb8efc.

* Revert "Roll Dart SDK from b8f4018535fa to 86c749398b3a (16 revisions) (#25999)"

This reverts commit a712ffe2.

We now build against a specific Windows SDK rather than whatever happens
to be installed on the host machine.

This also rolls the buildroot to include change
https://github.com/flutter/buildroot/pull/448, which generates the WinRT
headers from the CIPD Windows SDK.

This also rolls an updated version of cppwinrt that includes supports
for long paths.

This also re-enables the UWP builder.

* Roll buildroot to pick change to cppwinrt invocation

* disable uwp builders