Update secp256k1 subtree to upstream release 0.4.0

src/secp256k1/.github/actions/install-homebrew-valgrind/action.yml

@@ -0,0 +1,33 @@
+name: "Install Valgrind"
+description: "Install Homebrew's Valgrind package and cache it."
+runs:
+  using: "composite"
+  steps:
+    - run: |
+        brew tap LouisBrunner/valgrind
+        brew fetch --HEAD LouisBrunner/valgrind/valgrind
+        echo "CI_HOMEBREW_CELLAR_VALGRIND=$(brew --cellar valgrind)" >> "$GITHUB_ENV"
+      shell: bash
+
+    - run: |
+        sw_vers > valgrind_fingerprint
+        brew --version >> valgrind_fingerprint
+        git -C "$(brew --cache)/valgrind--git" rev-parse HEAD >> valgrind_fingerprint
+        cat valgrind_fingerprint
+      shell: bash
+
+    - uses: actions/cache@v3
+      id: cache
+      with:
+        path: ${{ env.CI_HOMEBREW_CELLAR_VALGRIND }}
+        key: ${{ github.job }}-valgrind-${{ hashFiles('valgrind_fingerprint') }}
+
+    - if: steps.cache.outputs.cache-hit != 'true'
+      run: |
+        brew install --HEAD LouisBrunner/valgrind/valgrind
+      shell: bash
+
+    - if: steps.cache.outputs.cache-hit == 'true'
+      run: |
+        brew link valgrind
+      shell: bash

src/secp256k1/.github/actions/run-in-docker-action/action.yml

@@ -0,0 +1,49 @@
+name: 'Run in Docker with environment'
+description: 'Run a command in a Docker container, while passing explicitly set environment variables into the container.'
+inputs:
+  dockerfile:
+    description: 'A Dockerfile that defines an image'
+    required: true
+  tag:
+    description: 'A tag of an image'
+    required: true
+  command:
+    description: 'A command to run in a container'
+    required: false
+    default: ./ci/ci.sh
+runs:
+  using: "composite"
+  steps:
+    - uses: docker/setup-buildx-action@v2
+
+    - uses: docker/build-push-action@v4
+      id: main_builder
+      continue-on-error: true
+      with:
+        context: .
+        file: ${{ inputs.dockerfile }}
+        tags: ${{ inputs.tag }}
+        load: true
+        cache-from: type=gha
+
+    - uses: docker/build-push-action@v4
+      id: retry_builder
+      if: steps.main_builder.outcome == 'failure'
+      with:
+        context: .
+        file: ${{ inputs.dockerfile }}
+        tags: ${{ inputs.tag }}
+        load: true
+        cache-from: type=gha
+
+    - # Tell Docker to pass environment variables in `env` into the container.
+      run: >
+        docker run \
+          $(echo '${{ toJSON(env) }}' | jq -r 'keys[] | "--env \(.) "') \
+          --volume ${{ github.workspace }}:${{ github.workspace }} \
+          --workdir ${{ github.workspace }} \
+          ${{ inputs.tag }} bash -c "
+            git config --global --add safe.directory ${{ github.workspace }}
+            ${{ inputs.command }}
+          "
+      shell: bash