deps: Bump to rand v0.9 where possible (#480)

* deps: Bump to rand v0.9 where possible

#### Problem

The repo is still on rand v0.8 in a lot of places, but that version
isn't very compatible with rust 2024 due to its usage of `gen` as a
function name, which is becoming a keyword.

#### Summary of changes

Follow https://rust-random.github.io/book/update-0.9.html to perform the
upgrade to rand v0.9 where possible.

Most crypto libraries are still on rand v0.8 / rand_core v0.6, and the
blstrs and ecdsa implementations of `random` aren't as simple as just
taking 32 or 64 random bytes, so I left those back.

* Also update getrandom for wasm builds

* wasm: Don't use cache fallback for CI

* Bump getrandom to next patch version

* Address nits

Author: joncinque

.github/workflows/main.yml

@@ -454,10 +454,9 @@ jobs:
         with:
           stable-toolchain: true
           cargo-cache-key: cargo-stable-wasm
-          cargo-cache-fallback-key: cargo-stable
 
       - name: Install wasm-pack
-        uses: taiki-e/cache-cargo-install-action@v2
+        uses: taiki-e/install-action@v2
         with:
           tool: wasm-pack