Draft release notes for 1.64

[joshtriplett]

Still needs lists of stabilized APIs.

[pietroalbini]

Thanks a lot for writing this! It seems that there is a bunch of stuff in the 1.64 release, but it seems to me we can maybe editorialize things a bit, emphasizing the most prominent features and de-emphasizing the other ones (maybe a list at the bottom of the post)?

[pietroalbini]

Pushed new changes to the blog post, with each individual change in its own commit. Roughly what I did:

• Changed the authorship to our usual "Rust Release Team"
• Moved items I feel like are less relevant to the wider audience to the "other changes" section. In the past we tried to keep around 3 big news items in the blog posts.
• Moved all the compatibility notes in its own section, for the same reason as above. I also shrinked a bit the transmute section while keeping its meaning.
• Added a note that this is the last release with RLS
• Moved IntoFuture as the first item, I feel that's more likely to change how people use Rust.
• Expanded the note about rust-analyzer with Eric's draft.
• Copied the stabilized APIs from the relnotes.

[joshtriplett]

All the changes seem reasonable to me. Added one commit to adjust some wording, but otherwise LGTM.