feat(aspen/emacs): Begin a complete emacs config revamp

I'm still on doom, but without all the cruft I've accumulated over the
last ~6 years it's actually good and fast and nice. Also, the config is
literate now!

The old emacs is still in .emacs.d, since occasionally I want to
reference it, but eventually I'll just get rid of it

Change-Id: Icda840d798594f7e6b188dba044494597d5f6043
Reviewed-on: https://cl.tvl.fyi/c/depot/+/10999
Reviewed-by: aspen <root@gws.fyi>
Tested-by: BuildkiteCI

users/aspen/emacs/snippets/rust-mode/benchmark

@@ -0,0 +1,10 @@
+# -*- mode: snippet -*-
+# name: benchmark
+# uuid: benchmark
+# key: bench
+# condition: t
+# --
+#[bench]
+fn ${1:benchmark_name}(b: &mut Bencher) {
+   `%`b.iter(|| $0);
+}