Support fileSize dependency injection across all theme-check usages

[albchu]

Overview

A subset of our remaining checks to migrate will need to know the file size. We need to make sure that all our theme-check usecases will support these checks.

This is supplemental work necessary to unblock the following checks:

Migrate asset_size_app_block_css Migrate asset_size_css Migrate asset_size_app_block_javascript Migrate asset_size_javascript

Acceptance Criteria

• [ ] Online-store-web code editor supports these checks properly
• [x] VSCode extension supports these checks properly
• [ ] CLI supports these checks properly