chore: reset filesToSync and filesToRemove when syncing on preview app

[Fatme]

In case when .js file is changed and after that .html file is changed, preview app is restarted on device. Actually {N} CLI needs to reset filesToSync after syncing on preview app.

PR Checklist

• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
• You have signed the CLA.
• All existing tests are passing: https://github.com/NativeScript/nativescript-cli/blob/master/CONTRIBUTING.md#contribute-to-the-code-base
• Tests for the changes are included.

What is the current behavior?

Preview app is restarted on .html change

What is the new behavior?

Preview app is not restarted on .html change

[Fatme]

run ci

[Fatme]

run ci