fixup! Run expensive tests regularly, but not on every pull request

.github/workflows/expensive_tests.yml

@@ -0,0 +1,25 @@
+name: Expensive tests
+
+on:
+  #schedule:
+  #  - cron: '0 */2 * * *'
+  push:
+    branches:
+      - hrxi/minor_fixes51
+  workflow_dispatch:
+
+jobs:
+  expensive-tests:
+    runs-on: ubuntu-22.04
+
+    steps:
+    - uses: actions/checkout@v4
+    - uses: dtolnay/rust-toolchain@stable
+      with:
+        toolchain: stable
+        components: llvm-tools-preview
+    - uses: Swatinem/rust-cache@v2
+    - name: Install cargo-nextest
+      run: curl -LsSf https://get.nexte.st/latest/linux | tar zxf - -C ${CARGO_HOME:-~/.cargo}/bin
+    - name: Run tests
+      run: cargo nextest run --features=expensive-tests,nimiq-zkp-component/test-prover