[Themes] Optimize theme polling to skip re-downloading recently uploaded files

[jamesmengo]

WHY are these changes introduced?

• Improves behaviour on https://github.com/Shopify/develop-advanced-edits/issues/203
• Enables the https://github.com/Shopify/develop-advanced-edits/issues/204

WHAT is this pull request doing?

Prevent an additional call to download theme assets when already present in the local theme.

How to test your changes?

1. Create a file only present locally on your theme
2. shopify-dev theme dev --theme-editor-sync --dev-preview
3. Select Upload local files to the remote theme
4. Wait for the success box
5. After ~3 seconds, you should NOT see something like this Synced: get 'templates/list-collections.alternate.json' from remote theme

Code.-.dawn_export.templates_list-collections.json.cli.Workspace.mp4

Measuring impact

How do we know this change was effective? Please choose one:

• n/a - this doesn't need measurement, e.g. a linting rule or a bug-fix
• Existing analytics will cater for this addition
• PR includes analytics changes to measure impact

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've made sure that any changes to dev or deploy have been reflected in the internal flowchart.

[github-actions]

Thanks for your contribution!

Depending on what you are working on, you may want to request a review from a Shopify team:

• Themes: @shopify/advanced-edits
• UI extensions: @shopify/ui-extensions-cli
  • Checkout UI extensions: @shopify/checkout-ui-extensions-api-stewardship
• Hydrogen: @shopify/hydrogen
• Other: @shopify/app-management

[github-actions]

Coverage report

St.❔	Category	Percentage	Covered / Total
🟡	Statements	71.97% (+0.01% 🔼)	7034/9774
🟡	Branches	68.81% (+0.02% 🔼)	3484/5063
🟡	Functions	71.44%	1881/2633
🟡	Lines	73.28% (+0.01% 🔼)	6632/9050

Test suite run success

1650 tests passing in 766 suites.

Report generated by 🧪jest coverage report action from ec084f7

[github-actions]

We detected some changes at either packages/*/src or packages/cli-kit/assets/cli-ruby/** and there are no updates in the .changeset.
If the changes are user-facing, run "pnpm changeset add" to track your changes and include them in the next release CHANGELOG.

[karreiro]

Thank you, @jamesmengo! Great stuff :)