feat: dialog for choosing contact source while editing merged contact (#201)

[Aga-C]

What is it?

• Bugfix
• Feature
• Codebase improvement

Description of the changes in your PR

• Modified edit button (both in contacts list and viewing contact) to ensure it doesn't trigger editing messenger contact while having merging contacts turned on (as described in [Bug] Can display, but not edit, (birth)dates from old phone #201 (comment)).
• To have common code for both places, I've moved finding duplicate contacts from ViewContactActivity to Activity extensions.
• As I couldn't reproduce the issue reported in [Bug] Can display, but not edit, (birth)dates from old phone #201, I've tested this feature by inverting conditions to always open the messenger contact. As it was working, I suppose that normal version of the code should also work.

Fixes the following issue(s)

• Fixes [Bug] Can display, but not edit, (birth)dates from old phone #201

Acknowledgement

• I read the contribution guidelines.

[naveensingh]

Yeah, let's go with a Choose contact to edit radio dialog. It'll be simpler that way.

[naveensingh]

_{^{You just couldn't let me skip this one, could ya? :)}}

Just three problems:

• The dialog should not show up when tapping a contact source at the bottom of the view contact screen. It's implicit in that case.
• The dialog should show up when Merge duplicate contacts is enabled and On contact click is set to Edit contact.
• The radio button ripple effect is being clipped. Why not just reuse RadioGroupDialog here? See SimpleActivity.showContactSourcePicker for example.

[naveensingh]

Works good now. Just made a change myself because I'm on a clock. Thanks!