fix(compat): convertLegacyVModelProps should merge model option in mixins

[moesoha]

If a Vue 2 component defines model option via mixins, convertLegacyVModelProps will not take care of it and break it.

[netlify]

✔️ Deploy Preview for vue-sfc-playground ready!

🔨 Explore the source changes: 2f3510a

🔍 Inspect the deploy log: https://app.netlify.com/sites/vue-sfc-playground/deploys/61ea58cbf64fc30007e795d8

😎 Browse the preview: https://deploy-preview-5251--vue-sfc-playground.netlify.app/

[netlify]

✔️ Deploy Preview for vuejs-coverage ready!

🔨 Explore the source changes: 2f3510a

🔍 Inspect the deploy log: https://app.netlify.com/sites/vuejs-coverage/deploys/61ea58cbfbf60300083a76e0

😎 Browse the preview: https://deploy-preview-5251--vuejs-coverage.netlify.app

[netlify]

✔️ Deploy Preview for vue-next-template-explorer ready!

🔨 Explore the source changes: 2f3510a

🔍 Inspect the deploy log: https://app.netlify.com/sites/vue-next-template-explorer/deploys/61ea58cb89a7d400076db6a1

😎 Browse the preview: https://deploy-preview-5251--vue-next-template-explorer.netlify.app

[yyx990803]

Added logic for recursive mixins with mixins.