feat: improve tab navigation and cycling

[nikvnt]

This PR includes commits based on the feature request from #8681

It sets up custom fields for tab navigation within the 'Keyboard Shortcuts' section and also introduces a new section with two radio options under 'Tab Management'. These options allow users to decide whether they should cycle through unloaded tabs while navigating with shortcuts. Additionally, this same configuration can be bound to a shortcut for quick toggling.

I am aware someone tried to add custom shortcuts for tab navigation many months ago, but it was discontinued and unfinished, so I've made this.

I attempted to set the default shortcuts for tab cycling to 'Ctrl + Tab' and 'Ctrl + Shift + Tab', so that people who were already used to those would not have to go through the struggle of setting these manually on the custom fields. However, the 'Ctrl + Shift + Tab' combination did not function as expected. Because of that, I've decided to leave these default keybinds undefined for the time being and submit this PR for Cheff to check it out.

The l10n PR related to this is right here.

[SheepDomination]

Cycling though unloaded tabs and loaded tabs is not bad. I like the idea of adding shortcuts too tabs but I feel that could get messy; unless you only apply it to a few tabs.

[nikvnt]

Cycling though unloaded tabs and loaded tabs is not bad. I like the idea of adding shortcuts too tabs but I feel that could get messy; unless you only apply it to a few tabs.

We already have the default shortcuts for tab cycling in general, which are ctrl + tab and ctrl + shit + tab. My implementation here merely improves that by allowing users to customize these however they'd prefer, like explained on #8681. And also like explained there, Zen does currently cycle through unloaded and loaded tabs by default. This particular implementation gives you control over that, giving you the option to choose whether you'd like to cycle that way, or only through the ones previously loaded.

[mr-cheffy]

The issue with using "key"s is that it wont take preference over the site, meaning that if a site prevents default behavior, people wont be able to switch tabs.

I still believe it should be a global preference

[mr-cheffy]

Looks good!