ci: add GitHub action to clean up runner disk space

Define a composite action to remove large toolsets, unused packages,
Docker images, and caches from the GitHub runner, freeing up disk space
for builds.

Note that this file is copied from the following `tapd` PR:
lightninglabs/taproot-assets#1878

Not all of the targeted files when running the script, should ever
have been used when building the binaries for LNC, but we keep the
script consistent between the repos for simplicity.

Author: ViktorT-11

.github/actions/cleanup-space/action.yaml

@@ -0,0 +1,50 @@
+name: "Clean up runner disk space"
+description: "Removes large, non-essential toolsets to free up disk space on the runner."
+
+runs:
+  using: "composite"
+  steps:
+    - name: Free up disk space
+      shell: bash
+      run: |
+        echo "Removing large toolsets to free up disk space..."
+        echo "Disk space before cleanup:"
+        df -h
+
+        # Remove dotnet to save disk space.
+        sudo rm -rf /usr/share/dotnet
+        # Remove android to save disk space.
+        sudo rm -rf /usr/local/lib/android
+        # Remove ghc to save disk space.
+        sudo rm -rf /opt/ghc
+        # Remove large packages.
+        sudo rm -rf /usr/share/swift
+        sudo rm -rf /usr/local/julia*
+        sudo rm -rf /opt/hostedtoolcache
+
+        # Remove docker images to save space.
+        docker image prune -a -f || true
+
+        # Remove large apt packages.
+        sudo apt-get remove -y \
+            '^aspnetcore-.*' \
+            '^dotnet-.*' \
+            '^llvm-.*' \
+            'php.*' \
+            '^mongodb-.*' \
+            '^mysql-.*' \
+            azure-cli \
+            google-chrome-stable \
+            firefox \
+            powershell \
+            mono-devel \
+            libgl1-mesa-dri 2>/dev/null || true
+        sudo apt-get autoremove -y
+        sudo apt-get clean
+
+        # Remove caches.
+        sudo rm -rf /usr/local/share/boost
+        sudo rm -rf "$AGENT_TOOLSDIRECTORY"
+
+        echo "Disk space after cleanup:"
+        df -h