Thoroughly update versions and methodology

For hash-pinned dependencies, adds comments documenting the associated
versions.

Adds a pin to `slither-analyzer` which was prior missing.

Updates to Monero 0.18.4.4.

`mimalloc` now has the correct option set when building for `musl`. A C++
compiler is no longer required in its Docker image.

The runtime's `Dockerfile` now symlinks a `libc.so` already present on the
image instead of creating one itself. It also builds the runtime within the
image to ensure it only happens once. The test to ensure the methodology is
reproducible has been updated to not simply create containers from the image,
yet rebuild the image entirely, accordingly. This also is more robust and
arguably should have already been done.

The pin to the exact hash of the `patch-polkadot-sdk` repo in every
`Cargo.toml` has been removed. The lockfile already serves that role,
simplifying updating in the future.

The latest Rust nightly is adopted as well (superseding
https://github.com/serai-dex/serai/pull/697).

The `librocksdb-sys` patch is replaced with a `kvdb-rocksdb` patch, removing a
git dependency, thanks to https://github.com/paritytech/parity-common/pull/950.

.github/workflows/reproducible-runtime.yml

@@ -27,7 +27,7 @@ jobs:
   build:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac
+      - uses: actions/checkout@1af3b93b6815bc44a9784bd300feb67ff0d1eeb3 # 6.0.0
 
       - name: Install Build Dependencies
         uses: ./.github/actions/build-dependencies