Rewrite ImportVCardActivity to Kotlin + Compose

[sdsantos]

Based on another branch. Compare diff: sdsantos/platform_packages_apps_Contacts@select-account...sdsantos:platform_packages_apps_Contacts:import-vcard

Closes #35

The ImportVCard user flow was simplified:

• Now the ImportVCardActivity is always the responsible for selecting the account
• The behavior no longer changes if it's called from an external app
• The import confirmation dialog was removed, and the confirmation is done by selecting the destination account, which is always shown, even if there's only one destination account

The user flow is now:

• Verifies and requests permissions if not granted
• Selects provided VCard file from another app, or opens the select files system screen
• Selects account
• Parses VCard(s) to verify if they are valid
• Starts background import

import_vcard.mp4