i3-sway: only return current user's socket

[nathantypanski]

Constrain the pgrep command to only return results for the current user.
Additionally, quote the socket variables to prevent splitting.

Previously, if multiple users on a system were running sway, the
pgrep used in finding swaySocket would return multiple results. As a
result, reloads of sway would fail.

Fixes #2912.

Description

Checklist

• Change is backwards compatible.

• Code formatted with ./format.

• Code tested through nix-shell --pure tests -A run.all.

  • I was only able to run the Sway tests because my local build is blocked by bug: The use of shellDryRun breaks my build #2693 as I don't currently use unstable:

    sway-bindkeys-to-code: OK
    sway-default: OK
    sway-followmouse: OK
    sway-followmouse-legacy: OK
    sway-modules: OK
    sway-no-xwayland: OK
    sway-null-config: OK
    sway-null-package: OK
    sway-post-2003: OK
    sway-workspace-default: OK
    sway-workspace-output: OK
    swaynag-empty-settings: OK
    swaynag-example-settings: OK
    

• Test cases updated/added. See example.

  • Not sure how to test this as it requires multiple users and home-manager normally only manages one user at a time. Happy to try to make a test case if someone can give me pointers.

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