ci: replace inline cleanup commands with reusable action

Update workflows to use the new `cleanup-space` composite action for
clearing runner disk space, replacing the manual `rm -rf` commands. Add
a cleanup step to the cross-compilation job.

Author: ViktorT-11

.github/workflows/main.yml

@@ -29,6 +29,9 @@ jobs:
       - name: git checkout
         uses: actions/checkout@v5
 
+      - name: Clean up runner space
+        uses: ./.github/actions/cleanup-space
+
       - name: go cache
         uses: actions/cache@v3
         with:
@@ -72,6 +75,9 @@ jobs:
         with:
           fetch-depth: 0
 
+      - name: Clean up runner space
+        uses: ./.github/actions/cleanup-space
+
       - name: go cache
         uses: actions/cache@v3
         with:
@@ -108,6 +114,9 @@ jobs:
       - name: git checkout
         uses: actions/checkout@v5
 
+      - name: Clean up runner space
+        uses: ./.github/actions/cleanup-space
+
       - name: go cache
         uses: actions/cache@v3
         with:
@@ -137,6 +146,9 @@ jobs:
       - name: git checkout
         uses: actions/checkout@v5
 
+      - name: Clean up runner space
+        uses: ./.github/actions/cleanup-space
+
       - name: go cache
         uses: actions/cache@v3
         with: