GHA: Reduce workflow load (#2902)

I think we can save some resources here and trigger some workflows less frequently.

Author: dweindl

.github/workflows/test_benchmark_collection_models.yml

@@ -24,7 +24,6 @@ jobs:
         extract_subexpressions: ["true", "false"]
     env:
       AMICI_EXTRACT_CSE: ${{ matrix.extract_subexpressions }}
-
     steps:
     - name: Set up Python ${{ matrix.python-version }}
       uses: actions/setup-python@v5
@@ -99,7 +98,7 @@ jobs:
       fail-fast: false
       matrix:
         python-version: [ "3.12" ]
-        extract_subexpressions: ["true", "false"]
+        extract_subexpressions: ["false"]
     env:
       AMICI_EXTRACT_CSE: ${{ matrix.extract_subexpressions }}
     steps:

.github/workflows/test_install.yml

@@ -1,5 +1,7 @@
 name: Installation
-on: [push, pull_request, merge_group, workflow_dispatch]
+on:
+  merge_group:
+  workflow_dispatch:
 
 jobs:
   archive:

.github/workflows/test_python_cplusplus.yml

@@ -1,6 +1,8 @@
 name: C++/Python Tests
 on:
   push:
+    branches:
+      - main
   merge_group:
   workflow_dispatch:
   pull_request:

.github/workflows/test_python_nogil.yml

@@ -1,7 +1,6 @@
 name: Python nogil Tests
 on:
   push:
-  pull_request:
     branches:
       - main
   merge_group:

.github/workflows/test_python_ver_matrix.yml

@@ -1,11 +1,5 @@
 name: Python Tests
 on:
-  push:
-    branches:
-      - main
-
-  pull_request:
-    branches:
   workflow_dispatch:
   merge_group:
   schedule: