Fix theme push --development --json to output the proper exit code

[karreiro]

Fix theme push --development --json command to output the proper exit code when an error occurs (#1353).

WHY are these changes introduced?

These changes aim to output exit code 1 when anything wrong happens during a theme push operation.

WHAT is this pull request doing?

This PR extracts error reporting logic from ShopifyCLI::Theme::Syncer and delegates it to ShopifyCLI::Theme::Syncer::ErrorReporter. At the error reporter level, we have the mechanism to identify if any error report has happened at that session.

Then, at the Theme::Command::Push level, we check if the syncer has reported any errors, and we finally provide the proper exit code.

How to test your changes?

1. Run the theme push command with the following parameters:

shopify theme push --development --json

2. Check exit code:

echo "Exit code: $?"

Here's the previous behavior:

Here's how it actual behavior (with this PR applied):

Post-release steps

Update checklist

• I've added a CHANGELOG entry for this PR (if the change is public-facing)
• I've considered possible cross-platform impacts (Mac, Linux, Windows).
• I've left the version number as is (we'll handle incrementing this when releasing).
• I've included any post-release steps in the section above.

[macournoyer]

Wowow! 👍 Nice refactoring too, again 🧹