Protobuf and gRPC Version Updates for Python 3.9 - 3.12

## Summary

Due to a critical security vulnerability ([CVE-2026-0994](https://nvd.nist.gov/vuln/detail/CVE-2026-0994)) discovered in `protobuf` versions prior to 5.29.6, we are updating the `protobuf` and `grpcio` dependencies in the Python Worker. This update will be rolled out with host version **4.1052** and may cause breaking changes for some Python function apps.

## What's Changing

The following dependency versions are being updated in the Azure Functions Python Worker:

- **protobuf**: `~=4.25.3` → `~=5.29.6`
- **grpcio**: `~=1.59.0` → `~=1.70.0`

## Who Is Affected

This change may affect you if:

- Your Python function app uses `protobuf` or `grpcio` directly in your code or dependencies
- Your app runs on **Python 3.9, 3.10, 3.11, or 3.12**
- You have pinned specific versions of `protobuf` or `grpcio` in your `requirements.txt` that are incompatible with the new versions

## Rollout Timeline

- **Host Version**: 4.1052
- **Expected Completion**: August 2026

## Potential Impact

After this update is deployed, function apps that depend on older versions of `protobuf` or `grpcio` may experience:

- Runtime errors or import failures
- Type incompatibilities if using protobuf-generated code compiled with older versions
- Breaking changes in gRPC functionality due to API changes between major versions

```
RuntimeError: The grpc package installed is at version 1.37.1, but the generated code in
FunctionRpc_pb2_grpc.py depends on grpcio>=1.70.0.
```

## Mitigation Options

### Option 1: Update Your Dependencies

Update your `requirements.txt` to use compatible versions:

```txt
protobuf~=5.29.6
grpcio~=1.70.0
```

### Option 2: Use Isolated Worker Dependencies

If you need to continue using older versions of `protobuf` or `grpcio`, you can set the `PYTHON_ISOLATE_WORKER_DEPENDENCIES` application setting to `1` to prioritize your app's pinned versions.

### Option 3: Migrate to Python >= 3.13

Migrate your existing function apps to run on Python 3.13 or Python 3.14.

No files, tests, or entry points are named. Start by locating the Python Worker's dependency declarations and checking how Python 3.9–3.12 dependencies are tested. Done means protobuf is updated to ~=5.29.6, grpcio to ~=1.70.0, and the affected worker test or compatibility checks pass.

Written by the indexing model from the issue text.