Add finalized FCPs to agenda

[spastorino]

This adds the finalized FCPs to the agenda.

It may be a good idea to use to-announce also in rust repo as soon as an FCP is accepted, and then I can just remove the label after adding it to the agenda. Otherwise, right now this dumps the following issues ...

• "BufReader should provide a way to seek without dumping the buffer" rust#31100
• "Allocator traits and std::heap" rust#32838
• "Tracking issue for std::sync::Once poisoning" rust#33577
• "Tracking issue for Vec::resize_with and resize_default" rust#41758
• "non-lexical lifetimes (NLL) tracking issue" rust#43234
• "Tracking issue: RFC 2103 - attributes for tools" rust#44690
• "extern type cannot support size_of_val and align_of_val" rust#49708
• "Tracking issue for Option::deref, Result::deref, Result::deref_ok, and Result::deref_err" rust#50264
• " Tracking issue for #![feature(maybe_uninit_ref)]" rust#63568
• "Stabilize the #[alloc_error_handler] attribute (for no_std + liballoc)" rust#66740
• "Make handle_alloc_error default to panic (for no_std + liballoc)" rust#66741
• "Stabilize core::panic::Location::caller" rust#72448
• "mv std libs to std/" rust#73265

But we want just show the new ones. Still this is good for now because I can manually edit the agenda output.

r? @Mark-Simulacrum