Improve --only/--ignore parameters on Theme pull/push commands to work without quotes

[karreiro]

WHY are these changes introduced?

The theme push command doesn't work as expected when partners use glob parameters like this: shopify theme push -d --only layout/*. However, it works when they run the same command with quotes shopify theme push -d --only "layout/*".

WHAT is this pull request doing?

Here's what happens from the ShopifyCLI::Options perspective when partners run the commands mentioned above:

$ shopify theme push -d --only "layout/*"
args: []
flags: {:development=>true, :only=>["layout/*"]}

$ shopify theme push -d --only layout/*
args: ["layout/theme.liquid"]
flags: {:development=>true, :only=>["layout/password.liquid"]}

This PR addresses this issue by relying on custom conversions to handle glob values in the Theme::Command::Pull and Theme::Command::Push classes.

How to test your changes?

• Open a theme
• Change something in the layout directory
• Run shopify theme push -d --only layout/* (without quotes)
• Notice that now the --only parameter works as expected

Before this PR

After this PR

Post-release steps

The documentation of --only and --ignore may mention that users can pass parameters with or without quotes.

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]

TIL about custom conversions!

[karreiro]

(rebasing the branch)

Thanks again for your PR (#2051), @kilgore5! Just an FYI, I've updated theme serve here, following your PR and also using the new RootHelper 🚀

[kilgore5]

@karreiro Awesome, thanks!