Replace black and flake8 with ruff for linting and formatting

- Remove .flake8; add [tool.ruff] and [tool.ruff.format] config in pyproject.toml
  (line-length 120, excludes, ignore list, per-file-ignores, mccabe complexity)
- Update GitHub workflow lint job to run `ruff check .` and `ruff format --check .`
- Swap black and flake8 for ruff in requirements.txt and Pipfile
- Change capnp/__init__.py to ruff-style noqa comment
- Move max-complexity into [tool.ruff.lint.mccabe], lint options into [tool.ruff.lint]
- Add per-file-ignores for capnp/__init__.py (F401, F403, F405), remove inline noqa
- Run ruff format across codebase (24 files) for consistent style

examples/async_ssl_client.py

@@ -33,21 +33,15 @@ async def main(host):
     addr, port = host.split(":")
 
     # Setup SSL context
-    ctx = ssl.create_default_context(
-        ssl.Purpose.SERVER_AUTH, cafile=os.path.join(this_dir, "selfsigned.cert")
-    )
+    ctx = ssl.create_default_context(ssl.Purpose.SERVER_AUTH, cafile=os.path.join(this_dir, "selfsigned.cert"))
 
     # Handle both IPv4 and IPv6 cases
     try:
         print("Try IPv4")
-        stream = await capnp.AsyncIoStream.create_connection(
-            addr, port, ssl=ctx, family=socket.AF_INET
-        )
+        stream = await capnp.AsyncIoStream.create_connection(addr, port, ssl=ctx, family=socket.AF_INET)
     except Exception:
         print("Try IPv6")
-        stream = await capnp.AsyncIoStream.create_connection(
-            addr, port, ssl=ctx, family=socket.AF_INET6
-        )
+        stream = await capnp.AsyncIoStream.create_connection(addr, port, ssl=ctx, family=socket.AF_INET6)
 
     client = capnp.TwoPartyClient(stream)
     cap = client.bootstrap().cast_as(thread_capnp.Example)