Force WG handshake each time the config is updated

[dlon]

Fix DES-1563

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This change is 

[MarkusPettersson98]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @dlon)

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talpid-wireguard/src/connectivity/mod.rs line 9 at r1 (raw file):

mod pinger;

pub use check::Cancellable;

⛏️ Technically this should be gated on android or force_wireguard_handshake? 🫠

Code quote:

pub use check::Cancellable;

[linear]

DES-1563 Investigate: Connecting takes 15 s with PQ on Windows

[MarkusPettersson98]

Reviewed 3 of 3 files at r2, all commit messages.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @dlon)

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talpid-wireguard/src/ephemeral.rs line 122 at r2 (raw file):

) -> Result<(), CloseMsg> {
    #[cfg(force_wireguard_handshake)]
    let _ = establish_tunnel_connection(tunnel, connectivity).await;

Would be nice with an explicit comment about why the return value is discarded. Obviously we care about the side effect of calling establish_tunnel_connection only.

Code quote:

    #[cfg(force_wireguard_handshake)]
    let _ = establish_tunnel_connection(tunnel, connectivity).await;