Fixes https://github.com/flutter/flutter/issues/112833 Most of the actual changes here are in [packages/flutter_tools/lib/src/version.dart](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605), while the rest is largely just addressing changes to the constructor of `FlutterVersion` which now has different dependencies. This change makes `FlutterVersion` an interface with two concrete implementations: 1. `_FlutterVersionGit` which is mostly the previous implementation, and 2. `_FlutterVersionFromFile` which will read a new `.version.json` file from the root of the repo The [`FlutterVersion` constructor](https://github.com/flutter/flutter/pull/124558/files#diff-092e00109d9e1589fbc7c6de750e29a6ae512b2dd44e85d60028953561201605R70) is now a factory that first checks if `.version.json` exists, and if so returns an instance of `_FlutterVersionFromGit` else it returns the fallback `_FlutterVersionGit` which will end up writing `.version.json` so that we don't need to re-calculate the version on the next invocation. `.version.json` will be deleted in the bash/batch entrypoints any time we need to rebuild he tool (this will usually be because the user did `flutter upgrade` or `flutter channel`, or manually changed the commit with git).
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