Add setup for writing tests for TunnelManager

[buggmagnet]

As the name implies, this PR makes TunnelManager testable. No tests have been ran just yet.

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This change is 

[rablador]

Reviewed 58 of 58 files at r1, all commit messages.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @buggmagnet)

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ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift line 39 at r1 (raw file):

        case .connected, .connecting, .reconnecting, .waitingForConnectivity(.noConnection), .error:
            guard var tunnel = interactor.tunnel else {

let should be fine here.

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ios/MullvadVPN/TunnelManager/Tunnel.swift line 23 at r1 (raw file):

}

protocol TunnelProtocol: AnyObject, Equatable {

There's quite a lot going on in this protocol. I understand that it's here mainly to facilitate testing (hence this PR), but maybe we should divide it into appropriate chunks now that we're abstracting things anyway?

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ios/MullvadVPNTests/RESTRequestExecutor+Stubs.swift line 36 at r1 (raw file):

        guard let success = success else { throw POSIXError(.EINVAL) }

        return try await withCheckedThrowingContinuation { continuation in

Simplify with return success()?

[buggmagnet]

Reviewable status: 56 of 58 files reviewed, 3 unresolved discussions (waiting on @rablador)

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ios/MullvadVPN/TunnelManager/Tunnel.swift line 23 at r1 (raw file):

Previously, rablador (Jon Petersson) wrote…

There's quite a lot going on in this protocol. I understand that it's here mainly to facilitate testing (hence this PR), but maybe we should divide it into appropriate chunks now that we're abstracting things anyway?

I agree, however it would be outside of the scope of this (already) large PR.
We should definitely do it in a follow up PR instead.

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ios/MullvadVPNTests/RESTRequestExecutor+Stubs.swift line 36 at r1 (raw file):

Previously, rablador (Jon Petersson) wrote…

Simplify with return success()?

Done.
I think in the future we will want to make this more configurable for advanced testing.

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ios/MullvadVPN/TunnelManager/StopTunnelOperation.swift line 39 at r1 (raw file):

Previously, rablador (Jon Petersson) wrote…

let should be fine here.

Done.

[rablador]

Reviewed 2 of 2 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved