Prevent /applications page from loading on large installations

[dee-kryvenko]

Summary

Add an option to disable /applications page without either a project and/or a namespace filter.

Motivation

On a large ArgoCD instances with 10k+ apps, the /applications landing page becomes basically unusable. Nor does it makes any sense. No one ever will act or perform bulk actions on 10k+ apps anyways. For people who do not understand how ArgoCD works, it makes them think that ArgoCD is bad or can't scale or having issues. By extension, it casts a shadow on the team that maintains ArgoCD instance unjustifiably. Although that in my opinion it's not an issue, or at least is not an actionable one and does not indicate any underlying issues with the platform. Kubectl will also suffer if someone does --all-namespaces action, and its not a default behavior for a good reason. From my experience, people often having no clue that their quality can be drastically improved should only they follow a simple practice of NOT visiting ArgoCD landing page without at least one filter being activated. Even when I have to switch filters, for example - switch to another project, I would usually select another project first and then and only then unselect the previous project. If I ever forget to do it - congrats to me, I just suddenly got extra time for an extra cup of coffee.

Proposal

For example, just pick a first project on the list if no filters are set. Or, if feature is enabled, and no filters are set - display a placeholder empty page with a message or something. Last filter selection is already being remembered in the browser, no need to store anything additionally. No need to enforce this on the backend neither - being purely a quality of life for the end user improvement, this can be just a UI only feature. Probably doesn't even need explicit configuration option - UI can just see that the apps count is > X, and bail out. Really don't care how exactly it will be done, just that this pretty small and insignificant issue creates too much noise and talks about platform in general.