Merge commit from fork

* [libesl] Validate `Content-Length` in `esl_recv_event`.

`atol()` accepted negative values, allowing a remote ESL peer to cause
a one-byte heap underwrite (`Content-Length: -1`) or NULL-pointer
dereference (`Content-Length: -2`, since `esl_assert` compiles out
under `NDEBUG`). Reject negative and oversized values, and check
`malloc` failure instead of relying on `assert`.

Cap at `ESL_MAX_CONTENT_LENGTH` (16 MiB).

* [libesl] Add test_recv_event.

.github/workflows/unit-test.yml

@@ -107,6 +107,13 @@ jobs:
         run: |
           ./run-tests.sh ${{ inputs.total-groups }} ${{ inputs.current-group }} --output-dir logs || exit 1
 
+      - name: Run libesl tests
+        if: ${{ inputs.current-group == 1 }}
+        shell: bash
+        working-directory: ${{ inputs.working-directory }}/../../libs/esl
+        run: |
+          make check
+
       - name: Collect unit test logs
         if: always()
         shell: bash