Fixing html snippet completion and integration tests

[alexgav]

HTML snippet completions were being included when they shouldn't have been

### Summary of the changes

• Include HTML snippet completions only when they request flag indicates they should be
• Also added a cohosting test, though this was not broken in cohosting

Fixes:

• Integration tests
• Snippets included when they shouldn't be (e.g. in a start tag)

[davidwengier]

Thanks for the quick fix