ci: bump upload-artifact v3 -> v4 for GitHub; drop Forgejo artifact support

GitHub deprecated actions/upload-artifact@v3. Forgejo's runner does not support
the stock @v4 (it requires a patched fork), so this intentionally breaks Forgejo
artifact upload -- acceptable while Forgejo support is dropped, the goal being a
green GitHub mirror. Artifact names already embed the matrix flavour, so v4's
unique-name-per-job requirement is already satisfied; there are no
download-artifact steps to update.

Author: brightprogrammer

.github/workflows/fuzz.yml

@@ -136,7 +136,7 @@ jobs:
         fi
         
     - name: Upload fuzzing results
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       if: always()
       with:
         name: fuzzing-results

.github/workflows/test-linux-arm64.yml

@@ -78,7 +78,7 @@ jobs:
 
     - name: Upload test logs
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-logs-linux-arm64-${{ matrix.flavour }}
         path: build/meson-logs/testlog.txt

.github/workflows/test-linux.yml

@@ -108,7 +108,7 @@ jobs:
 
     - name: Upload test logs
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-logs-linux-${{ matrix.flavour }}
         path: build/meson-logs/testlog.txt

.github/workflows/test-macos.yml

@@ -100,7 +100,7 @@ jobs:
 
     - name: Upload test logs
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-logs-macos-${{ matrix.flavour }}
         path: build/meson-logs/testlog.txt

.github/workflows/test-windows-llvm.yml

@@ -205,7 +205,7 @@ jobs:
       # the artifact we have no way to tell a green run with N tests
       # from a green run with 0 tests.
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-logs-windows-llvm-${{ matrix.flavour }}
         path: build/meson-logs/testlog.txt

.github/workflows/test-windows-msvc.yml

@@ -58,7 +58,7 @@ jobs:
       # the artifact we have no way to tell a green run with N tests
       # from a green run with 0 tests.
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: test-logs-windows-msvc
         path: build/meson-logs/testlog.txt