(improvement) unit tests for benchmarking query planning.

[mykaul]

Not a very scientific one, but reasonable to get some measurements in terms of how different optimizations work. Example run (on #650 branch):

  warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
============================================================================================================ test session starts ============================================================================================================= platform linux -- Python 3.14.2, pytest-8.3.5, pluggy-1.6.0 rootdir: /home/ykaul/github/python-driver
configfile: pyproject.toml
plugins: asyncio-1.1.0, anyio-4.12.1
asyncio: mode=Mode.STRICT, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function collected 4 items

tests/unit/test_policy_performance.py Pinned to CPU 0 ....

=== Performance Benchmarks ===
Policy                         | Ops        | Time (s)   | Kops/s
----------------------------------------------------------------------
DCAware                        | 100000     | 0.2328     | 429
RackAware                      | 100000     | 0.3637     | 274
TokenAware(DCAware)            | 100000     | 1.5884     | 62
TokenAware(RackAware)          | 100000     | 1.6816     | 59
----------------------------------------------------------------------

Pre-review checklist

• I have split my patch into logically separate commits.
• All commit messages clearly explain what they change and why.
• I added relevant tests for new features and bug fixes.
• All commits compile, pass static checks and pass test.
• PR description sums up the changes and reasons why they should be introduced.
• I have provided docstrings for the public items that I want to introduce.
• I have adjusted the documentation in ./docs/source/.
• I added appropriate Fixes: annotations to PR description.

[mykaul]

Latest commit add Host policy. Now it looks like this:

ykaul@ykaul:~/github/python-driver$ pytest -s tests/unit/test_policy_performance.py 
/usr/lib/python3.14/site-packages/pytest_asyncio/plugin.py:211: PytestDeprecationWarning: The configuration option "asyncio_default_fixture_loop_scope" is unset.
The event loop scope for asynchronous fixtures will default to the fixture caching scope. Future versions of pytest-asyncio will default the loop scope for asynchronous fixtures to function scope. Set the default fixture loop scope explicitly in order to avoid unexpected behavior in the future. Valid fixture loop scopes are: "function", "class", "module", "package", "session"

  warnings.warn(PytestDeprecationWarning(_DEFAULT_FIXTURE_LOOP_SCOPE_UNSET))
==================================================================================================================================================== test session starts =====================================================================================================================================================
platform linux -- Python 3.14.2, pytest-8.3.5, pluggy-1.6.0
rootdir: /home/ykaul/github/python-driver
configfile: pyproject.toml
plugins: asyncio-1.1.0, anyio-4.12.1
asyncio: mode=Mode.STRICT, asyncio_default_fixture_loop_scope=None, asyncio_default_test_loop_scope=function
collected 6 items                                                                                                                                                                                                                                                                                                            

tests/unit/test_policy_performance.py Pinned to CPU 0
......

=== Performance Benchmarks ===
Policy                         | Ops        | Time (s)   | Kops/s    
----------------------------------------------------------------------
DCAware                        | 100000     | 0.0989     | 1010      
Default(DCAware)               | 100000     | 0.1532     | 652       
HostFilter(DCAware)            | 100000     | 0.3303     | 302       
RackAware                      | 100000     | 0.1149     | 870       
TokenAware(DCAware)            | 100000     | 0.2112     | 473       
TokenAware(RackAware)          | 100000     | 0.2249     | 444       
----------------------------------------------------------------------