Alt shortcuts sometimes letting through key presses

[Garmelon]

Issue description

When a CPU-intensive application runs, alt-based keyboard shortcuts are sometimes let through to the programs running in the panes instead of being captured by zellij.

So far, I've observed key press leakage with the shortcuts alt+h, alt+l, alt+[], alt+f. I could not observe leaks with any ctrl-based shortcuts.

Minimal reproduction

Steps 1 to 4 can probably replaced by any other way to get 100% CPU usage on all cores. The program generating the CPU load does not need to run in zellij.

1. Clone https://github.com/Garmelon/blamegraph
2. Clone a big repo (e.g. https://github.com/NixOS/nix)
3. In the blamegraph repo, run cargo run --release -- /tmp/bgdata gather path/to/nix
4. Wait until the progress bars appear (may take a minute or two)
5. Open a new zellij session
6. Try various alt-based keyboard shortcuts, eg. switching between panes
7. Observe that sometimes, the key presses are handled by zellij and sometimes they are handled by the underlying program running in the focused pane

Blamegraph will, after an initial period of analyzing the git repo, call git blame in parallel on all cores, which usually takes close to 100% of each core.

Other relevant information

System info: Arch linux, Gnome (Wayland), Gnome terminal, zellij 0.41.2

For bonus points, run cargo run --release -- /tmp/bgdata graph-years years.html after you've reproduced the bug :D