[flutter_tools] generate empty plugin registrants for winuwp and fix local engine for winuwp_ (#79827)

[flutter_tools] separate concept of null safe language version from current language version (#79052)

* Revert "Enable dart_plugin_registry_test (#76645)"

This reverts commit 109e0bb9.

* Revert "Apply changes caused by https://github.com/flutter/flutter/pull/76662 (#77093)"

This reverts commit cdca6485.

* Revert "Disable clang format in the plugin registrants (#76662)"

This reverts commit dadbd47d.

* Revert "Disable warnings for the dart plugin registrant (#76561)"

This reverts commit 098ece52.

* Revert "Remove dart_plugin_registry_test timeouts (#76838)"

This reverts commit 1610a274.

* Revert "Implement dartPluginClass support for plugins (#74469)"

This reverts commit b7d48062.

Kick.

flutter_tool: DeferredComponent and LoadingUnit classes, Manifest deferred-components parsing (#75394)

This reverts commit 8b6baae4.

Our current top crasher is an unclear error when ProcessManager fails to resolve an executable path. To fix this, we'd like to being adjusting the process resolution logic and adding more instrumentation to track failures. In order to begin the process, the ProcessManager has been folded back into the flutter tool

= gets escaped into %3D which seems to be tripping up cmake on windows since % is a control character. Switch to base64 encoding, since this does not have % nor , in the output character set.

This change is not trivially cherry pickable, and isn't tested on windows aside from my local, manual tests due to the planned CI work not being complete yet.

Fixes #75017
Fixes #74705