Migrate CI to Github Actions (#1884)

Changes the CI system from Jenkins to Github Actions (GHA) like we did for OoT

This is an adaptation of the Jenkinsfile we have and the solution made by @Dragorn421 for OoT

Relevant OoT PRs:
- https://github.com/zeldaret/oot/pull/2740
- https://github.com/zeldaret/oot/pull/2742
- https://github.com/zeldaret/oot/pull/2754

New features include:
- Not needing to selfhost a runner
  - Required private stuff for building is hosted on a private repo
- Building multiple versions in parallel
  - Our old jenkinsfile wasn't building `n64-jp-1.1`. Even if it doesn't match right now, I think it is important checking a PR doesn't completely break it.
- Run bss fixer in CI
- Upload mapfiles as build artifacts

This specific approach to handle GHA for decomp projects was adapted from the one used by the GC/Wii community. It is documented here https://github.com/encounter/dtk-template/blob/main/docs/github_actions.md There's a writeup about this adaptation for N64 projects [here](https://github.com/AngheloAlf/drmario64/pull/19).

.github/actions/fix-bss-and-generate-patch/action.yml

@@ -0,0 +1,20 @@
+inputs:
+  version:
+    required: true
+
+runs:
+  using: composite
+  steps:
+    - name: Fix BSS
+      shell: sh
+      run: .venv/bin/python3 tools/fix_bss.py -v ${{ inputs.version }}
+
+    - name: Generate patch
+      shell: sh
+      run: git diff > fix_bss_${{ inputs.version }}.patch
+
+    - name: Upload patch
+      uses: actions/upload-artifact@v7
+      with:
+        name: fix_bss_${{ inputs.version }}.patch
+        path: fix_bss_${{ inputs.version }}.patch