ivtest: Integration of regression tests into the build system

Replace .github/test.sh with a unified set of targets installed
via `make check-*` in ivtest/, thereby removing CI-specific test
coordination. This avoids duplication in the regression logic and
ensures consistent execution between local and CI environments.
PLI1-dependent tests are now correctly controlled via
`configure --enable-libveriuser`.

Currently, the regression suite still depends on an iverilog package,
which must be installed manually at the location specified with
`configure --prefix=*`. Afterward, the complete regression suite
(VVP, VPI, and Python tests) can be run via `make check-installed`
and individual checks can be run with `check-installed-vpi`,
`check-installed-vvp` and `check-installed-vvp-py`.

.github/workflows/test.yml

@@ -34,7 +34,8 @@ jobs:
         sudo make install
 
     - name: Test
-      run: ./.github/test.sh
+      run: |
+        make check-installed
 
 
   lin:
@@ -64,7 +65,8 @@ jobs:
         sudo make install
 
     - name: Test
-      run: ./.github/test.sh
+      run:
+        make check-installed
 
     - name: Documentation
       run: |
@@ -120,11 +122,7 @@ jobs:
 
     - name: Test
       run: |
-        if [ ${{ matrix.msystem }} = "CLANG64" ] ; then
-            ./.github/test.sh no-pli1
-        else
-            ./.github/test.sh
-        fi
+        make check-installed
 
     - uses: actions/upload-artifact@v4
       with: