BIP459: Add vendored secp256k1lab library

Add a vendored copy of the secp256k1lab library (master branch, commit
a265da139aea27386085a2a8760f8698e1bda64e) that the full-aggregation
reference implementation and test vector scripts depend on.

bip-0459/secp256k1lab/.github/workflows/main.yml

@@ -0,0 +1,34 @@
+name: Tests
+on: [push, pull_request]
+jobs:
+  ruff:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install the latest version of uv
+        uses: astral-sh/setup-uv@v5
+      - run: uvx ruff check .
+  mypy:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.11", "3.12", "3.13", "3.14"]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install the latest version of uv, setup Python ${{ matrix.python-version }}
+        uses: astral-sh/setup-uv@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - run: uvx mypy .
+  unittest:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        python-version: ["3.11", "3.12", "3.13", "3.14"]
+    steps:
+      - uses: actions/checkout@v4
+      - name: Setup Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+      - run: python3 -m unittest