Migrate from Webpack to Vite

[ChristophWurst]

Describe the task

Vite shows better frontend performance due to better tree shaking and therefore lighter bundles and less js to load and parse for the browser.

Affected components

• Calendar: perf: bundle with vite calendar#6068
• Contacts: perf: migrate to vite contacts#3804
• Mail: perf: bundle with vite mail#9757
• nextcloud/calendar-availability-vue: chore: build package with vite calendar-availability-vue#68
• nextcloud/calendar-js: feat!: bundle with vite and ship cjs instead of umd bundle calendar-js#733
• nextcloud/cdav-library: Bundle with vite cdav-library#900

To do

• Do