Description

Setting the min flutter sdk version to 1.20.0
After 1.20.0, newly created plugins won't contain no-op iOS folders. Which requires the sdk version to be 1.20.0 or above.

WARNING
Landing this PR before 1.20 release will have below impacts:

• For people who is on stable (1.17)
  • Plugin author will be fine to create new plugins, the plugin won't have 1.20.0 constraints.
  • App authors will not be able to use plugins that are newly created by people who are on master. They will see an error about version solving failed.
• For people who is on beta (1.20.0-7.X.pre)
  • Plugin author will be fine to create new plugins, the plugin won't have 1.20.0 constraints.
  • App authors will not be able to use plugins that are newly created by people who are on master. They will see an error about version solving failed.
• For people who is on master
  • Plugin author will be fine to create new plugins.
  • App authors will be fine to use the newly created plugins.

Related Issues

#60215

Tests

I added the following tests:

newly created plugin has min flutter sdk version as 1.20.0

Checklist

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• I read the Contributor Guide and followed the process outlined there for submitting PRs.
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• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
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• I updated/added relevant documentation (doc comments with ///).
• All existing and new tests are passing.
• The analyzer (flutter analyze --flutter-repo) does not report any problems on my PR.
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Breaking Change

Did any tests fail when you ran them? Please read Handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.
• Yes, this is a breaking change. If not, delete the remainder of this section.
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