Config `rust-analyzer` to use the new formatting style

[rami3l]

OTOH to facilitate use in IDEs so that we can never worry about reorganizing imports, I'm discovering the feasibility of adding a recommended rust-analyzer config that looks like so:

rustfmt = { extraArgs = { "+nightly", "--config-path=.rustfmt.unstable.toml" } },

Interesting, I cannot use that yet because rust-analyzer is calling rustfmt at the source file's basedir so .rustfmt.unstable-toml will be "not found":

• Recursive --config-path doesn't recurse rustfmt#4660

Originally posted by @rami3l in #5065

[rami3l]

More about the expected rustfmt design: rust-lang/rustfmt#4660 (comment)

[rami3l]

I've made rust-lang/rustfmt#7115 hoping to properly settle this issue.