Build LLVM for Windows (#248)

This PR changes the CI build scripts to also build LLVM for windows.
**It doesn't build `revive` itself for windows**. This will come in a
follow up. But once we have a LLVM binary release the turn around time
will be much quicker for experimenting with the revive windows build.

I manually uploaded the release those changes produce
[here](https://github.com/paritytech/revive-alex-workflowtest/releases/tag/llvm-18.1.8-revive.22f3ceb).
This enables this PR's CI to find the proper release. This is necessary
because I am also making changes to the folder structure and artifact
naming that the other CI jobs are depending on.

Releases generated from this branch can be inspected here:
https://github.com/paritytech/revive-alex-workflowtest/releases/tag/v0.1.0-dev.12

Summary of changes:
- Change `llvm-builder` to use MSVC toolchain on windows
- Fix `llvm-builder` to work with `.exe` files
- Unify the llvm release jobs into a single one. This removed a lot of
copy pasted code and also speeds up the build by giving each their own
runner.
- Use the LLVM target triple to name the binary releases instead of an
ad-hoc naming convention
- Remove the nested folder hierarchy inside the llvm release. Its just
now a single folder `llvm-<target>` that contains the toolchain.
- Give jobs and workflows consistent names
- Replace all runners bei their `*-latest` counterpart
- Only use `parity-large` to build llvm now. All other jobs use github
runners

.github/actions/get-emsdk/action.yml

@@ -1,4 +1,4 @@
-name: "get emsdk"
+name: "Get Emscripten SDK"
 inputs:
   version:
     description: ""
@@ -9,7 +9,6 @@ inputs:
 runs:
   using: "composite"
   steps:
-
     - name: install emsdk
       shell: bash
       run: |
@@ -17,4 +16,4 @@ runs:
         cd emsdk
         git checkout tags/${{ inputs.version }}
         ./emsdk install ${{ inputs.version }}
-        ./emsdk activate ${{ inputs.version }}
+        ./emsdk activate ${{ inputs.version }}