Bruno Leroux 8d837062a4
Add InputDecorator.error to allow error message customization (#129275)
## Description

This PR is a fork of https://github.com/flutter/flutter/pull/118610 with some changes (mainly applying @justinmc comments).

~~This can be used by KishanBusa8 to update https://github.com/flutter/flutter/pull/118610 or can become a non WIP PR if KishanBusa8 does not respond or can not work on the update.~~

## Related Issue

fixes https://github.com/flutter/flutter/issues/11068

## Tests

Adds 3 tests.
2023-06-28 14:57:15 +00:00
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