Add a dedicated search page to Rustdoc

[Gankra]

Search is lazily loaded after the rest of the content on a given page. This makes searches, especially ones using in-browser search utilities, or jumping through search history really sluggish and unresponsive. A dedicated empty page optimized for this usecase would be greatly appreciated.

[Gankra]

Related to #17296

[steveklabnik]

Triage: no change.

[steveklabnik]

@rust-lang/rustdoc is this a feature we plan to implement?

[GuillaumeGomez]

Isn't the search efficient enough now? If more search functionalities are wanted, we can always add them though.

[kzys]

+1 for resolving. Rustdoc is not that slow (or our machines are faster, compared to 2014).

For the standard library, the landing page now has a small search box.

[camelid]

I'm not quite sure what this issue is requesting, and it does seem like the problem is resolved now. Shall we close the issue?

[GuillaumeGomez]

Funnily enough, we will end up with something like that once our plan started with #90630 will be done.
So yes, closing.