fix(vue): improve v-model integration for Vue 3.1.0+

[liamdebeasi]

Pull request checklist

Please check if your PR fulfills the following requirements:

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)
• Build (npm run build) was run locally and any changes were pushed
• Lint (npm run lint) has passed locally and any fixes were made for failures

Pull request type

Please check the type of change your PR introduces:

• Bugfix
• Feature
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Documentation content changes
• Other (please describe):

What is the current behavior?

Vue 3.1.0 introduced a minor breaking change to improve consistency between Vue 2 and Vue 3. Previously, properties there were unused did not show up as keys in the props object. Starting in Vue 3.1.0, all properties will show up regardless of whether or not they are used. In the Vue Output Targets, we check for the presence of modelValue, the v-model property by checking if the key exists in the props object. This no longer works as it was always there in Vue 3.1.0

More context: vuejs/core#3889

What is the new behavior?

• In addition to checking for the presence of the v-model key, we also check to see if it is undefined or not.

Does this introduce a breaking change?

• Yes
• No

Other information