[Contact picker] Look for an actual account in case of email address

[giomfo]

Your use case

When I open the contact picker to start a new DM, and type an email address, Element-iOS doesn't check whether an actual account is discoverable for this email

Element-Android triggers a lookup request to replace this email address with a potential actual account

There is multiple advantages to discover user on email here:

• the end user has the confirmation their contact has a matrix account
• we work on a new flow to create DM only on the first message https://github.com/vector-im/element-ios/issues/5864, select a matrix id is more powerful than an email in this case
• prevent the application from creating a new DM whereas one is already created for this user

Have you considered any alternatives?

No response

Additional context

No response