Fix inconsistent spacing between paragraphs

[rablador]

A few places in the app has inconsistent spacing between paragraphs. This PR addresses that and creates a common style to share.

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This change is 

[linear]

IOS-732 Fix the abnormal spacing between lines in the device info after account creation

[rablador]

Reviewable status: 0 of 10 files reviewed, 1 unresolved discussion

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ios/MullvadVPN/Coordinators/ApplicationCoordinator.swift line 416 at r1 (raw file):

            guard let self else { return }
            router.dismissAll(.primary, animated: true)
            DispatchQueue.main.async {

Opportunistically fixed an unrelated bug where logging out from add voucher screen would crash due to doing UI work on background thread.

[buggmagnet]

Reviewed 9 of 10 files at r1.
Reviewable status: 9 of 10 files reviewed, 2 unresolved discussions (waiting on @rablador)

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ios/MullvadVPN/View controllers/VPNSettings/CustomDNSViewController.swift line 116 at r1 (raw file):

                domains or websites known for distributing ads, malware, trackers and more. \
                This might cause issues on certain websites, services, and apps.

I think this new line was intentionally there

Before

After

[rablador]

Reviewable status: 9 of 10 files reviewed, 2 unresolved discussions (waiting on @buggmagnet)

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ios/MullvadVPN/View controllers/VPNSettings/CustomDNSViewController.swift line 116 at r1 (raw file):

Previously, buggmagnet wrote…

I think this new line was intentionally there

Before

After

Fixed

[buggmagnet]

Reviewed 1 of 10 files at r1, 4 of 4 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions