Swift: added trapgen

This checks in the trapgen script generating trap entries in C++.

The codegen suite has been slightly reorganized, moving the templates
directory up one level and chopping everything into smaller bazel
packages. Running tests is now done via
```
bazel run //swift/codegen/test
```

With respect to the PoC, the nested `codeql::trap` namespace has been
dropped in favour of a `Trap` prefix (or suffix in case of entries)
within the `codeql` namespace. Also, generated C++ code is not checked
in in git any more, and generated during build. Finally, labels get
printed in hex in the trap file.

`TrapLabel` is for the moment only default-constructible, so only one
single label is possible. `TrapArena`, that is responsible for creating
disjoint labels will come in a later commit.

.github/workflows/swift-codegen.yml

@@ -13,18 +13,18 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
+      - uses: ./.github/actions/fetch-codeql
+      - uses: bazelbuild/setup-bazelisk@v2
       - uses: actions/setup-python@v3
         with:
           python-version: '~3.8'
           cache: 'pip'
-      - uses: ./.github/actions/fetch-codeql
-      - uses: bazelbuild/setup-bazelisk@v2
-      - name: Install dependencies
+      - name: Install python dependencies
         run: |
           pip install -r swift/codegen/requirements.txt
       - name: Run unit tests
         run: |
-          bazel test //swift/codegen:tests --test_output=errors
+          bazel test //swift/codegen/test --test_output=errors
       - name: Check that code was generated
         run: |
           bazel run //swift/codegen

.github/workflows/swift-qltest.yml

@@ -29,6 +29,13 @@ jobs:
       - uses: actions/checkout@v3
       - uses: ./.github/actions/fetch-codeql
       - uses: bazelbuild/setup-bazelisk@v2
+      - uses: actions/setup-python@v3
+        with:
+          python-version: '~3.8'
+          cache: 'pip'
+      - name: Install python dependencies
+        run: |
+          pip install -r codegen/requirements.txt
       - name: Build Swift extractor
         run: |
           bazel run //swift:create-extractor-pack